Each Wednesday, the U.S. Army Marksmanship Unit (USAMU) publishes a reloading “how-to” article on the USAMU Facebook page. This week the USAMU’s reloading gurus addressed a question frequently asked by prospective handloaders: “How much neck tension is optimal, and how should I select a neck bushing size?” The USAMU offers a straight-forward answer, suggesting that hand-loaders start with a neck bushing that sizes the neck so that it is .003″ less than the loaded outside diameter with bullet in place. From there, you can experiment with more or less tension, but this is a good starting point for many popular cartridge types.
Determining Optimal Case-Neck Tension
This week, we examine determining the correct case neck tension for optimum accuracy. Our method is simple, but relies on the use of case sizing dies which accept interchangeable neck diameter bushings graduated in 0.001″ increments. (Those readers using fixed-diameter dies with expander balls aren’t forgotten, however. Methods of tailoring these dies for proper neck tension will be found below.)
In our experience across many calibers, sizing case necks 0.003″ under the loaded-case neck diameter usually yields excellent accuracy. In other words, the sized case neck expands 0.003″ when the bullet is seated.
Bushing Choice for Optimal Sizing
Over the years, we have periodically experimented with increasing neck tension to possibly improve accuracy. In testing with machine rests at 300/600 yards, accuracy often deteriorated as neck tension increased; thus, 0.003″ expansion (from sized neck to loaded neck) is where we usually start.
Using the .260 Remington as an example, our loaded cartridge case necks measure 0.292”. Simply subtract 0.003” from that, and use a bushing that sizes necks to 0.289” (after springback). There are exceptions — sometimes, brass may be a bit soft or hard. Some case necks might need, say, 0.001” more tension, but in general, this works well.
This .003″ standard of neck tension works very well for single-loaded, long range cartridges. Depending on your caliber and firearm, it MAY also work very well for magazine-fed cartridges. If this neck tension proves inadequate for your purpose, one can increase neck tension as needed while monitoring for possible accuracy changes.
Special Considerations for Coated Bullets: If you are using moly-coated bullets, this significantly reduces the “grip” of the case neck on the bullet, and you can expect to have to tighten your case necks accordingly — particularly for magazine-fed ammunition. In any event, we do not crimp rifle cartridges, and advise against it for accuracy handloads.
Tips for Using Expander Balls
Many savvy handloaders avoid the use of expander balls in high-accuracy reloading, if possible. These can stretch cases and/or disturb the concentricity of the case neck vs. case body. If using a die with an expander ball, tapering both ends of the ball and polishing it to a mirror finish can significantly reduce these effects. (Special carbide expander ball/decapping stem sets are available for this as well.)
The typical dies used with expander balls are intended to take any cases the user may find, and size them down well below the ideal “spec” to ensure any cases will give good neck tension. The necks are then expanded up to provide heavy to medium neck tension as the expander ball exits the neck. The brass is over-worked, leading to premature work-hardening, and seated-bullet concentricity may suffer. However, the cartridges produced are perfectly adequate for most handloaders. Those who seek finest accuracy generally prefer not to over-work their brass if possible.
Another Option — Custom-Honed FL Dies
There are companies which offer to convert one’s standard dies to accept neck bushings, and that gives excellent flexibility. Another, more “old-school” approach, is to have the neck of one’s FL die honed out to the desired diameter for sizing, based on one’s case neck thickness. The expander ball may then be reduced until it barely touches the case necks after sizing, or it may be eliminated entirely. However, once performed, this modification is permanent and leaves fewer options than the bushing route, if one later changes case neck thickness.
Those shooters who turn their case necks for optimum neck wall thickness uniformity, or for a tight-neck chamber, will want to take the reduced neck wall thickness into consideration. For example, when setting up a 7mm match rifle to use a standard hunting die without an expander ball, the slightly thinner necks resulted in a perfect 0.003″ reduction in the fired-neck diameter. The result was a low-cost die that fit with custom precision and yielded excellent, match accuracy!
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Here is the view from 9500 feet ASL. The SRS in 7mm Rem SAUM almost outran the Swarovski laser…
7mm RSAUM in a bolt-action bullpup? Yes it works. A talented shooter, who calls himself “ColdboreMiracle” in social media, has a Desert Tech SRS bullpup rifle chambered for the 7mm SAUM, and it hammers. The 7mm Remington SAUM (Short Action Ultra Magnum) is popular with F-Open competition shooters. It can also work well for long-range hunting and tactical tasks. Learn more about the 7mm Remington SAUM in our 7mm Cartridge Guide.
ColdboreMiracle explains how he selected the 7mm Rem SAUM chambering for his Desert Tech SRS Bullpup: “I just did a comparison between barrel life, velocity, brass, etc. and came to the SAUM. I can tell you this, if you go with one for your SRS, make sure you use long bullets like the 183 or 195, and seat them long. That will aid in smooth cycling.”
Mr. ColdboreMiracle tested the new generation 183gr Sierra MatchKings (item # 1983). These impressive projectiles are “tipped” at the factory. Claimed G1 BC is a lofty 0.707 (at 2300 fps and above). We have heard other reports that these bullets “hold waterline” exceptionally well at 1000 yards. That indicates the bullet-to-bullet BC is very consistent. No doubt the factory uniforming/pointing of the bullet tips helps in that regard.
As you can see, these 183-grainers shoot well in ColdboreMiracle’s SRS rifle. Here are five shots at 100 yards. That’s very impressive for a tactical-style rifle shot from a field-type bipod.
ColdboreMiracle says: “This is the only reason I need to shoot Sierra bullets. On the right (above) you can see the results of the 183gr SMK from my 7mm SAUM. Five shots at 100. A huge thanks to Mark at Short Action Customs, LLC for [chambering this barrel] for my Desert Tech SRS.”
ColdboreMiracle says the bullpup design has many advantages: “The Stealth Recon Scout (SRS) rifle from Desert Tech is a bullpup-configured precision rifle with a shorter length than many carbines. The SRS has a multitude of barrel options that can be swapped in under a minute — all of them come with a 1/2-MOA accuracy guarantee and return to zero. The SRS’s bullpup design puts the rifle’s COG closer to the shoulder, making the rifle balance better off-hand. The straight-line geometry of the SRS makes recoil seem lighter, and barrel hop is reduced, allowing the shooter to stay on target better. It takes a little getting used to, when converting from a traditionally-configured bolt gun. But once you do, you won’t go back.” To learn more about this rifle (and other Desert Tech arms), visit ColdboreMiracle’s Facebook Page and YouTube Channel.
7mm Remington SAUM — Key Considerations
In some respects, the 7mm SAUM cartridge may be better than the 7mm WSM. The 7mm SAUM holds less powder — but that’s a good thing, since the capacity is more than adequate to do the job. You can drive the 180s at 3000 fps with a SAUM using less powder than with a WSM. Additionally, the SAUM case has a slightly longer neck. This gives you greater flexibility in bullet seating. With a long neck you can set the throat so the long 180+ graing bullets are above the neck shoulder junction, yet you can still seat shorter hunting bullets close to the lands. Additionally, long case necks, some believe, cause less throat erosion than shorter necks. That’s not “hard science” but it is certainly a view shared by many experienced shooters. The long neck is one reason many varminters favor the 6mm Remington over the .243 Winchester.
7mm RSAUM Is More Efficient than 7mm WSM
7mm RSAUM shooter Steven Ikeeda tells us: “I decided that some type of 7mm was the ticket for doing well at 1000-yard matches, especially if one could drive the high-BC bullets at 2900+ fps. Looking over various 7mm cartridges that could produce those velocities (and didn’t require case-forming), I was impressed by the 7mm SAUM and the 7mm WSM. According to the load manuals, the 7mm WSM offered a bit more velocity than the 7mm SAUM. However, to achieve its small velocity advantage, the larger 7mm WSM had to burn 7-10% more powder than the 7mm SAUM. (The 7mm WSM has 81.0 grains of capacity vs. 73.6 grains for the 7mm SAUM.) The SAUM is a very efficient case. It looks like a 6.5×47 Lapua on steroids.”
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Here’s a great gift for Father’s Day that any dad with a truck should appreciate. Forum member John Niemi crafts custom hitch covers that look like the end of a cartridge case, complete with head-stamp. Costing $75.00 (delivered), they are made out of solid brass with a stainless steel “primer”. The diameter of the brass is 4 inches and the engraved letters are about half an inch tall. The section that slides over the trailer hitch is aluminum, so you don’t have to worry about rust.
The “headstamp” can include your favorite cartridge-maker and caliber (wildcats too!), or you can include the name of your business. John tells us: “I can engrave any text on one as long as there is enough room for it. Turn around time is usually less then a week after payment. I have sold many of these and everyone has been extremely happy with the quality and workmanship that I put into my product. These make great one-of-a-kind gifts.”
$75.00 Delivered in the USA
The current price for brass bullet hitch covers from John Niemi is $75.00 shipped anywhere in the USA. To order, send email to JohnNiemi [at] charter.net or call (503) 440-1954. John said he should be able to offer pretty quick turn-around, unless he just gets swamped this week.
Forum member Wayne (aka WAMBO) ordered a custom hitch cover from John, featuring the 30/338 Lapua Improved wildcat he calls the 300 WAMBOMAG. Wayne reports: “The hitch cover is very well made. I’m impressed with the quality. Buy with confidence.”
We’ve seen John’s craftsmanship on many of these hitches, and we can confirm that the hitches are beautifully made, and make a handsome addition to any vehicle. If you order one (or more), be sure to mention you learned about the hitch covers on AccurateShooter.com.
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At the request of our readers, we provide select “Deals of the Week”. Every Monday morning we offer our Bargain selections. Here are some of the best deals on firearms, hardware, reloading components, and shooting accessories. Be aware that sale prices are subject to change, and once clearance inventory is sold, it’s gone for good. You snooze you lose.
The Ruger Precision Rifle has been one of the hottest-selling long guns in America since its releases. It has pretty much been sold out for months. And Ruger just bumped the price on the new Gen2 edition up to $1599.00 MSRP. The Superstore got hold of some of some Gen 1 production RPRs in .243 Winchester. These rifles are IN STOCK and on sale for $1049.50. That’s a great price. The venerable .243 Win cartridge is a good choice for this rifle — Gavin Gear of UltimateReloder.com has an RPR chambered in .243 Win that has proven very accurate.
2. Monmouth Reloading — 1000 Lake City 5.56 Cases, $68.95
1000 pieces of Lake City brass for under seventy bucks? Yep, that’s a deal and a half. Monmouth Reloading is selling genuine, once-fired Lake City 5.56x45mm brass, thick-walled and sourced direct from the U.S. Military. Monmouth reports: “Our current stock of Lake City 5.56 looks to be all newer year Lake City head stamp but may contain a small percentage of other NATO headstamps. Lake City is a popular, reliable brass, normally capable of many reloads.” Monmouth includes 1% overage to account for any damaged brass. NOTE: Brass has crimped primers, so the pockets will need to be reamed or swaged prior to reloading.
3. Midsouth Shooters Supply — All Berger Bullets Now 10% Off
Need super-high-quality match, hunting, or varmint bullets? Then visit Midsouth Shooters Supply. Now through June 13, 2016, Midsouth has placed its entire stock of Berger Bullets on sale. You can save 10% off Midsouth’s already competitive prices, even on Berger’s most popular projectiles, such as the 6mm 105gr Match Hybrid, 6.5mm 130g Matcrh AR Hybrid, and the ultra-high BC 7mm 180gr Match Hybrid.
4. CDNN Sports — HK 416 .22LR Rimfire Rifle, $379.99
If you are looking for an AR-type .22 LR rifle for cross-training and rimfire tactical matches, the HK 416 is a fine choice. Made by Walther under license, these HK 416 D145RS rimfire rifles are accurate and reliable. This is a good deal at $379.99! The HK 416 normally sells for $550.00 to $600.00. One purchaser writes: “Great .22. I have had this gun a couple of months and have put about 500 rounds of 5 different brands of ammo through it. Not one FTE. I have shot other brands that can’t get through one 30-round mag without a failure.” CLICK HERE for Product Details.
5. Natchez — Hornady 22-Cal Varmint Bullets, $9.99 Per 100
Headed out for a varmint safari soon? Need inexpensive bullets for your .223 Rem or 22-250? Then check out this deal on Hornady 55-grainers from Natchez. Get 100 Soft Point .224-Caliber FB bullets for just $9.99. At that price, it doesn’t hurt so much when you shoot 1000+ rounds over a weekend. With good expansion, these bullets work great on prarie dogs and other small critters. Note: These sale bullets ship in a bag, not the box as shown.
6. Amazon.com — Howard Leight Electronic Earmuffs $40.97
Every shooter should own a pair of Electronic muffs, even if you prefer shooting with earplugs and/or standard muffs. Electronic muffs are great when you are doing spotting duties or are working near the firing line. They allow you to hear ordinary conversations while still providing vital hearing protection. Right now Amazon.com has the Howard Leight Impact Sport Electronic Muffs on sale for just $40.97. This is good deal — these NRR 22 muffs are currently Amazon’s #1 seller in the category. NOTE: For regular, sustained shooting we recommend muffs and/or earplugs with a higher NRR rating.
7. Natchez — RCBS ChargeMaster Dispenser, $279.99
Here’s a very good deal on the popular RCBS ChargeMaster combo scale/powder dispenser. This unit sells elsewhere for up to $389.00. You may want to act quickly as sale pricing changes frequently. This item is also available on Amazon.com for $296.99 with free shipping for Prime members.
8. Harbor Freight – 8-Drawer Wood Tool Chest
This Wood Tool Chest makes a great addition to your reloading room. The eight (8) drawers can hold the many small tools and accessories used for hand-loading, such as bushings, shims, uniforming tools, mandrels, neck-turners and more. A deeper top compartment (under the lid) holds wrenches and other larger tools. The price is just $79.99. A lockable sliding wood panel fits in place to cover the drawers when not in use. This locking panel also secures the drawers during transport.
9. Bullets.com — Handgun Safe $49.95
This pistol safe keeps your handguns secure while still permitting instant “push-button” access. The three-button lock can be personalized with 3- to 8-digit codes, and there is a key override. This safe will hold two (2) full-sized pistols and can also store passports, cash, or other valuables. The spring-loaded door gives you near-instant response. The all-steel case also includes mounting holes for fixing the safe to floor or shelf.
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What’s the best book for folks getting started in metallic cartridge reloading? According to our Forum members, the best manual for “newbie” reloaders is the Lyman Reloading Handbook. In our Shooters’ Forum, a newcomer to reloading was looking for a basic reloading guide that also included load data. The most recommended book was the Lyman Handbook, now in its 50th Edition (just released). Along with “how-to” advice on reloading procedures, the Lyman Manual features cartridge specifications and load data for the most popular cartridges.*
Here are some comments from Forum members:
“The Lyman book is an excellent manual with a large section describing the process of reloading. I heartily recommend it. As a beginning reloader, you may want to consider purchasing more than one book in order to get different perspectives on the reloading regimen. One can never be too careful. A ‘minor’ mistake can be costly.” — Cort
“In my opinion, the Lyman Manual is one of the best for the beginning reloader since it covers all the basics and some advanced methods. If possible, you would be also well served to hook up with an experienced reloader, preferably a target shooter or long-range varmint hunter, who can also give you some very useful pointers on precision reloading.” – K22
Editor’s NOTE: K22 echoes the advice we give to new hand-loaders. We suggest that novices find an experienced mentor who can “show them the ropes” and guide them through the basics.
Another gun blogger agrees that the Lyman Manual is a logical choice for new handloaders:
Carteach Review: The Lyman Reloading Manual
“[Lyman publishes] an excellent manual for any handloader, but especially for those new to the craft. Perhaps the best judgment of a handloader’s regard for a reloading manual is which one he chooses to give someone new to the fold. The needs of a new reloader differ from those of someone with long experience, and the right manual can set the foundation for years of safe procedures. Here is the one I choose to give a good friend embarking down the path:”
Carteach adds: “Lyman has always taken pains to provide very clear and understandable instruction on the basic process of reloading cartridges. The imaging is helpful and to the point. The load data Lyman provides is comprehensive, and [Lyman] takes the time to note special circumstances which new loaders need to be aware of. As example, the .30-06 section has some words regarding the M-1 Garand and its special needs. For someone who has never loaded for the Garand, these few sentences are golden!”
*We recommend that you always double-check printed load data with the latest web-based data from the actual powder manufacturers. Powder properties can change. The most current powder data is usually found on the powder-makers’ websites.
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If you wonder how ammo is made, starting with raw metal, check out this video from Hornady. It shows how bullet jackets are formed from copper, followed by insertion of a lead core. The jacket is then closed up over the core with the bullet taking its final shape in a die (a cannelure is applied on some bullet types). Next the video shows how cartridge brass is formed, starting with small cups of brass. The last part of the video shows how cases are primed and filled with powder, and how bullets are seated into the cases, using an automated process on a giant assembly-line. CLICK Link below to watch video:
At its 100,000+ square foot factory in Grand Island, Nebraska, Hornady produces millions of rounds of ammunition annually. The Grand Island factory is open for tours Monday through Thursday. Hornady Manufacturing, which now boasts over 300 employees, was founded by Joyce Hornady in 1949. The business is currently run by his son Steve Hornady who took over after his father’s death in a plane crash in 1981.
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Need top-quality 6mm match bullets for your 6mmBR, 6mm Dasher, 6XC, 6mm Creedmoor, 6-6.5×47, or .243 Win? Then get out your checkbook, because this is a very good deal on hard-to-find Berger 6mm 105gr Hybrid Match Bullets.
Right now Precision Reloading offers big, 500-count boxes of 105gr 6mm Hybrids for just $159.99. That works out to just $31.99 per 100, a lot less than you’d pay normally. These .243-diameter premium bullets hold many records and have won many important shooting competitions. You may want to act quickly — supplies are limited. When Precision Reloading runs out of sale inventory, prices will go up. To order, visit PrecisionReloading.com
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Each Wednesday the USAMU offers tips for handloaders on the USAMU Facebook page. This article from the “Handloading Hump-Day” archives should interest pistol competitors, an any shooter who enjoys getting the best possible accuracy from their fine pistols. In this article, the USAMU’s experts share key tips that can help optimize your pistol ammo. Follow this tips to produce more consistent ammo, that can shoot higher scores.
Optimize the Taper Crimp
One often-overlooked aspect of handloading highly-accurate pistol ammunition is the amount of crimp and its effect on accuracy. Different amounts of taper crimp are used with various handloads to obtain best accuracy. The amount is based on bullet weight, powder burn rate and charge, plus other factors. It is not unusual for our Shop to vary a load’s crimp in degrees of 0.001″ and re-test for finest accuracy.
Use Consistent Brass
Brass is also important to pistol accuracy. While accurate ammunition can be loaded using brass of mixed parentage, that is not conducive to finest results, particularly at 50 yards. It is important for the serious competitor/handloader to use brass of the same headstamp and ideally one lot number, to maximize uniformity. Given the volumes of ammunition consumed by active pistol competitors, using inexpensive, mixed surplus brass for practice, particularly at the “short line” (25 yards), is understandable. However, for the “long line” (50 yards), purchasing and segregating a lot of high-quality brass to be used strictly for slow-fire is a wise idea.
Importance of Uniform COAL
Uniformity of the Case Overall Length (COAL) as it comes from the factory is also important to achieving utmost accuracy. More uniform case lengths (best measured after sizing) contribute to greater consistency of crimp, neck tension, ignition/burn of powder charge, and so on. Cartridge case-length consistency varies from lot to lot, as well as by maker. Some manufacturers are more consistent in this dimension than others. [Editor’s note: It is easy to trim pistol brass to uniform length. Doing this will make your taper crimps much more consistent.]
Primers and Powders — Comparison Test for Accuracy
Pay attention to primer brands, powder types and charges. Evaluating accuracy with a Ransom or other machine rest at 50 yards can quickly reveal the effect of changes made to handload recipes.
Bullet Selection — FMJ vs. JHP
Bullets are another vital issue. First, there is the question of FMJ vs. JHP. A friend of this writer spent decades making and accuracy-testing rifle and pistol bullets during QC for a major bullet manufacturer. In his experience, making highly-accurate FMJ bullets is much more difficult than making highly-accurate JHPs, in large part due to the way the jackets are formed. Small die changes could affect accuracy of FMJ lots dramatically.
The CMP now allows “safe, jacketed ammunition” in Excellence-in-Competition (EIC) Service Pistol matches, although wadcutter ammunition is prohibited. Thus, the option to use very accurate JHP designs simplifies the life of CMP Service Pistol shooters in pursuit of the prestigious Distinguished Pistol Shot badge.
Hopefully, these tips will be helpful to any pistol shooters interested in accurate handloads, not just “Bullseye” shooters. Small tweaks to one’s normal routine can pay big dividends in improved accuracy and make practice and competition more rewarding.
Stay safe, and good shooting!
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It’s not easy to place a first shot on target at 1500 yards. You must measure the wind speed with precision, know your exact muzzle velocity, and have a sophisticated ballistics solver. In this short video from Ryansrangereport.com, the shooter manages a first-round hit on a steel silhouette at 1500 yards. He used a Kestrel 4500 NV Weather Meter with Applied Ballistics software to figure out the trajectory for his 6.5 Creemoor rounds.
The Kestrel recorded a wind velocity, and the internal software calculated a solution of 17 Mils elevation (that’s 928 inches of drop) with 2.5 Mils windage. “Bang” — the shooter sends it, and 2.6 seconds later “Clang” he had a hit (flight time was 2.6 seconds). Bryan Litz observes: “This is the science of accuracy (in the form of an Applied Ballistics Kestrel) being put to good use at 1500 yards”.
Later in the video (1:05-1:15) the shooter places three rounds on steel at 1000 yards in just 10 seconds. The three shots all fall within 10″ or so — pretty impressive for rapid fire. The shooter reports: “[In my 6.5 Creedmoor] I’m using a 136gr Lapua Scenar L. This bullet has impressed me. It screams out of my barrel at 2940 fps and holds on all the way out to 1,500 yards.”
The rifle was built by Aaron Roberts of Roberts Precision Rifles (RPRifles.com). Chambered for the 6.5 Creedmoor, it features a Leupold Mark VI 3-18x44mm scope.
The .22 Long Rifle (.22 LR) round is widely regarded as a relatively weak cartridge with very little penetrating power. Compared to most centerfire ammo that’s certainly true. But the venerable .22 LR actually packs more punch than you might expect. A recent test by rimfire specialist 22Plinkster demonstrated that the little .22 LR has enough power to drive a bullet through multiple walls.
In this video, 22Plinkster tests two types of .22 Long Rifle ammo, seeing how far a .22 LR bullet will pass through sheets of 1/2″-thick drywall. He shoots CCI Velocitor and CCI Stinger ammo types from both a pistol and a rifle. The results may surprise you. Shot from a pistol, the CCI Stinger ammo penetrated Nine (9) drywall sheets. Out of the rifle, the CCI Velocitor Ammo passed through Eleven (11) sheets, while the CCI Stinger stuck in the eleventh board, after passing through Ten (10) sheets.
The rimfire ammo’s penetrating power surprised .22 Plinkster: “I was really surprised that [the ammo] went through as many [dry wall boards] as it did. I was thinking four, maybe five tops …” He points out that the rifle penetration of 11 sheets was “equivalent to five walls, maybe six walls. If you were shooting in your house, and you had 1/2″ drywall, it would go through five walls. Now, that’s pretty scary that a .22 Long Rifle could do that.”
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We know many of our readers aren’t 100% clear on the difference between a secant ogive bullet and a tangent ogive bullet. Add the “blended” or “hybrid” ogive into the design equation and you add to the confusion. In this article, Berger Ballistician Bryan Litz, explains the characteristics of the three popular ogive types: tangent, secant, and hybrid.
In discussions of ballistics, you’ll see references to “tangent” and “secant” bullet shapes. For many readers, these terms can be confusing. To add to the confusion, bullet makers don’t always identify their projectiles as secant or tangent designs. This article provides a basic explanation of tangent and secant designs, to help you understand the characteristics of both bullet shapes.
Tangent vs. Secant vs. Hybrid
Most match bullets produced today use a tangent ogive profile, but the modern VLD-style bullets employ a secant profile. To further complicate matters, the latest generation of “Hybrid” projectiles from Berger Bullets feature a blended secant + tangent profile to combine the best qualities of both nose shapes. The secant section provides reduced drag, while the tangent section makes the bullet easier to tune, i.e. less sensitive to bullet seating depth position.
Berger Bullets ballistician Bryan Litz explains tangent and secant bullet ogive designs in a glossary section of his Applied Ballistics website, which we reprint below. Bryan then explains how tangent and secant profiles can be combined in a “hybrid” design.
How Bullet Ogive Curves are Defined
While the term “ogive” is often used to describe the particular point on the bullet where the curve reaches full bullet diameter, in fact the “ogive” properly refers to the entire curve of the bullet from the tip to the full-diameter straight section — the shank. Understanding then, that the ogive is a curve, how is that curve described?
LITZ: The ogive of a bullet is usually characterized by the length of its radius. This radius is often given in calibers instead of inches. For example, an 8 ogive 6mm bullet has an ogive that is a segment of a circular arc with a radius of 8*.243 = 1.952”. A .30-caliber bullet with an 8 ogive will be proportionally the same as the 8 ogive 6mm bullet, but the actual radius will be 2.464” for the .30 caliber bullet.
For a given nose length, if an ogive is perfectly tangent, it will have a very specific radius. Any radius longer than that will cause the ogive to be secant. Secant ogives can range from very mild (short radius) to very aggressive (long radius). The drag of a secant ogive is minimized when its radius is twice as long as a tangent ogive radius. In other words, if a tangent ogive has an 8 caliber radius, then the longest practical secant ogive radius is 16 calibers long for a given nose length.”
Ogive Metrics and Rt/R Ratio
LITZ: There is a number that’s used to quantify how secant an ogive is. The metric is known as the Rt/R ratio and it’s the ratio of the tangent ogive radius to the actual ogive radius for a given bullet. In the above example, the 16 caliber ogive would have an Rt/R ratio of 0.5. The number 0.5 is therefore the lowest practical value for the Rt/R ratio, and represents the minimum drag ogive for a given length. An ogive that’s perfectly tangent will have an Rt/R ratio of 1.0. Most ogives are in between an Rt/R of 1.0 and 0.5. The dimensioned drawings at the end of my Applied Ballistics book provide the bullets ogive radius in calibers, as well as the Rt/R ratio. In short, the Rt/R ratio is simply a measure of how secant an ogive is. 1.0 is not secant at all, 0.5 is as secant as it gets.
Hybrid Bullet Design — Best of Both Worlds?
Bryan Litz has developed a number of modern “Hybrid” design bullets for Berger. The objective of Bryan’s design work has been to achieve a very low drag design that is also “not finicky”. Normal (non-hybrid) secant designs, such as the Berger 105gr VLD, deliver very impressive BC values, but the bullets can be sensitive to seating depth. Montana’s Tom Mousel has set world records with the Berger 105gr VLD in his 6mm Dasher, but he tells us “seating depth is critical to the best accuracy”. Tom says a mere .003″ seating depth change “makes a difference”. In an effort to produce more forgiving high-BC bullets, Bryan Litz developed the hybrid tangent/secant bullet shape.
Bryan Litz Explains Hybrid Design and Optimal Hybrid Seating Depths
Story sourced by Edlongrange.
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Shiny brass — it may not shoot more accurately, but it does make you feel better about your hand-loaded ammo. While it’s not necessary to get brass “bright and shiny” after every firing, it is a good idea to clean powder residue, grime, and grit off your brass before you run cases into sizing dies. There are many ways to clean cartridge cases. A quick wipe with solvent on a patch may suffice for recently-shot cases. Older brass with baked-on carbon may require lengthy tumbling. Ultrasonic cleaning is another popular option that gets your brass clean inside and out.
Sinclair International has a series of helpful videos on brass cleaning. These short “how-to” videos, hosted by Bill Gravatt, Sinclair’s past President, cover the various processes you can use — tumbling, ultrasonic cleaning, chemical cleaning, and cleaning by hand.
Video ONE — Cleaning Brass in Vibratory or Rotary Tumbler
TIP: Brass that has recently been shot will clean more easily than brass that has been sitting many days or weeks. If your tumbling media is fresh the job should be done in an hour or less. It’s your choice whether to tumble with primers removed or with primers still in the cases. If you choose to tumble with primers out, we suggest you deprime with a depriming die, rather that put dirty brass into your sizing die. Some people like to add a teaspoon of liquid polish to the media. This does work, cutting tumble time, and making your brass more shiny. However, if you add liquid polish, do that BEFORE you add the brass and let the tumbler run for a 15 minutes to get the polish completely mixed into the media. Otherwise you can else up with gooey gunk inside your cases — a very bad thing.
Video TWO — Ulstrasonic Case Cleaning
TIP: There are many different types of solutions you can use. Soapy water suffices for some folks, particularly if you add a little Lemi-Shine. The Hornady and Lyman solutions work well, and can be used multiple times, provided you strain the solution to remove dirt and grit after cleaning sessions. Many ultrasonic cleaning machines have timers. Experiment with dwell time to see how long you need to immerse your brass. A very small amount of Ballistol in the solution will help lubricate your necks on the inside. This can make bullet seating go more smoothly, with more consistent neck tension.
Video THREE — Chemical Cleaners (Soaking without Ultrasound)
TIP: After using chemical cleaners, such as the Iosso solution, you need to water-rinse your brass thoroughly. A kitchen strainer helps with this (see video at 0:20). Also, don’t forget your brass in the chemical solution — follow the manufacturers recommendations and don’t exceed the recommended dwell time. Chemical cleaners work surprisingly well to remove grease and grime, and the solution can be re-used multiple times. However, if you want your cases to look bright and shiny (like new brass), you will probably have to tumble. [Editor: A very effective new chemical cleaner is the Brass Monkey product from the makers of Wipe-Out and Carb-Out. Add a teaspoon to a gallon of water then soak your brass for 20-30 minutes. It really works — the cases clean up dramatically].
Video FOUR — Manual Cleaning (By Hand)
TIP: Keep some oversize patches in your range kit. At the end of your shooting sessions, wipe off your fired brass with a patch dampened with a mild, non-corrosive solvent (once again Ballistol works well). Before the carbon sets up on your brass it is very easy to remove. For tougher jobs, you can use 0000 Steel Wool (as Bill recommends in the video). You may find that timely hand-cleaning lets you avoid tumbling altogether — or you may choose to tumble (or ultra-sound) your brass only after a half-dozen or so firings.
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The wait is over… Creedmoor Sports is now producing some of the best .223 Rem target ammo you can buy. Three “match-grade” types are offered with Sierra bullets and NEW Lake City cartridge brass. If you shoot Service Rifle, you may find that this new Creedmoor ammo rivals good handloads — and that’s quite an achievement. Creedmoor General Manager Dennis DeMille, a past National Service Rifle Champion, states: “As a National Rifle Champion and having fired probably a Gazillion rounds down range (mostly hand loads), I would not hesitate to compete with this ammunition on a National Level!”
Creedmoor currently offers .223 Rem competition ammo loaded with three of the most popular projectiles: 69 grain Sierra TMK (Tipped MatchKing), the 77 grain Sierra TMK, and the 77 grain Sierra BTHP. All three ammo types are loaded in Creedmoor’s new production facility using brand new Lake City Brass. As with all Creedmoor Ammo, each lot is pressure tested and velocity tested prior to every round being hand-inspected and packaged. That gives you confidence that this ammo is consistent lot to lot. Given the quality of this ammo, it is VERY affordable, starting at $34.75 per 50-round box. That works out to $0.69 per round. At that price, when you consider hand-loading, you have to ask yourself “what’s your time worth”? Would that time be better spend practicing?
Quantity Discounts and FREE Shipping on Large Orders
Creedmoor offers quantity discounts on the .223 Rem ammo: “Order Five (5) or more boxes of any one round to get your first price break. Order Ten (10) boxes of ANY combination of Creedmoor Ammo (Rifle or Pistol, Mix and Match) you get free shipping.”
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There’s an all-new book from Applied Ballistics. Modern Advancements in Long Range Shooting – Volume II, is now available for pre-order from the Applied Ballistics eStore. This 356-page hardcover resource is chock full of information, much of it derived through sophisticated field testing. The pre-order price is $34.95, $5.00 off the regular $39.95 price. The books are expected to ship in July, 2016.
AUDIO FILE: Bryan Litz Talks about Modern Advancements in Long Range Shooting, Volume 2. (Sound file loads when you click button).
Volume II of Modern Advancements in Long Range Shooting contains all-new content derived from research by Applied Ballistics. Author Bryan Litz along with contributing authors Nick Vitalbo and Cal Zant use the scientific method and careful testing to answer important questions faced by long range shooters. In particular, this volume explores the subject of bullet dispersion including group convergence. Advanced hand-loading subjects are covered such as: bullet pointing and trimming, powder measurement, flash hole deburring, neck tension, and fill ratio. Each topic is explored with extensive live fire testing, and the resulting information helps to guide hand loaders in a deliberate path to success. The current bullet library of measured G1 and G7 ballistic coefficients is included as an appendix. This library currently has data on 533 bullets in common use by long range shooters.
Bryan tells us that one purpose of this book is to dispel myths and correct commonly-held misconceptions: “Modern Advancements in Long Range Shooting aims to end the misinformation which is so prevalent in long range shooting. By applying the scientific method and taking a Myth Buster approach, the state of the art is advanced….”
Bullet Dispersion and Group Convergence
Part 1 of this Volume is focused on the details of rifle bullet dispersion. Chapter 1 builds a discussion of dispersion and precision that every shooter will benefit from in terms of understanding how it impacts their particular shooting application. How many shots should you shoot in a group? What kind of 5-shot 100 yard groups correlate to average or winning precision levels in 1000 yard F-Class shooting?
Chapter 2 presents a very detailed investigation of the mysterious concept of group convergence, which is the common idea that some guns can shoot smaller (MOA) groups at longer ranges. This concept is thoroughly tested with extensive live fire, and the results answer a very important question that has baffled shooters for many generations.
Part 2 of this Volume is focused on various aspects of advanced hand-loading. Modern Advancements (Vol. II) employs live fire testing to answer the important questions that precision hand loaders are asking. What are the best ways to achieve MVs with low ES and SD? Do flash hole deburring, neck tension, primer selection, and fill ratio and powder scales sensitivity make a difference and how much? All of these questions are explored in detail with a clear explanation of test results.
One of the important chapters of Part 2 examines bullet pointing and trimming. Applied Ballistics tested 39 different bullet types from .224 through .338 caliber. Ten samples of each bullet were tested for BC in each of the following configurations: original out of the box, pointed, trimmed, pointed and trimmed. The effect on the average BC as well as the uniformity in BC was measured and tabulated, revealing what works best.
Part 3 covers a variety of general research topics. Contributing author Nick Vitalbo, a laser technology expert, tested 22 different laser rangefinders. Nick’s material on rangefinder performance is a landmark piece of work. Nick shows how shooters can determine the performance of a rangefinder under various lighting conditions, target sizes, and reflectivities.
Chapter 9 is a thorough analysis of rimfire ammunition. Ballistic Performance of Rifle Bullets, 2nd Edition presented live fire data on 95 different types of .22 rimfire ammunition, each tested in five different barrels having various lengths and twist rates. Where that book just presented the data, Chapter 9 of this book offers detailed analysis of all the test results and shows what properties of rimfire ammunition are favorable, and how the BCs, muzzle velocities and consistency of the ammo are affected by the different barrels.
Chapter 10 is a discussion of aerodynamic drag as it relates to ballistic trajectory modeling. You will learn from the ground up: what an aerodynamic drag model is, how it’s measure and used to predict trajectories. Analysis is presented which shows how the best trajectory models compare to actual measured drop in the real world.
Finally, contributing author Cal Zant of the Precision Rifle Blog presents a study of modern carbon fiber-wrapped barrels in Chapter 11. The science and technology of these modern rifle barrels is discussed, and then everything from point of impact shift to group sizes are compared for several samples of each type of barrel including standard steel barrels.
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Ever wonder how (and where) Sierra tests its bullets? The answer is underground, in a 300-meter test tunnel located under Sierra’s factory in Sedalia, Missouri. The photo above shows the construction of the tunnel back in May, 1990. Like most bullet manufacturers, Sierra does live-fire bullet testing to ensure that Sierra projectiles perform as promised, with repeatable accuracy. Sierra’s 300-meter test range is the longest, privately-owned underground bullet test facility in the world. Sierra offers free tours of the test tunnel as part of Sierra’s Factory Tour Program.
Sierra Bullets tests every new bullet design and each lot of bullets. Sierra tells us: “When [we] change to a new bullet they are continually shooting them until they get the bullet properly set up and running and the range releases them to run (meaning the bullets shoot to spec). [Testers] are required to shoot at any lot change and periodically throughout the lot … even if it is just a press operator change. Lot sizes can vary from 5,000 to over 100,000 thousand. If anything changes — it is a new lot. When a new operator comes on — it is a new lot.”
Bevy of Barreled Actions for Bullet Testing
Sierra Bullets uses dozens of barreled actions for testing bullets. These barreled actions are clamped in stout, return-to-battery test fixtures. These heavy test fixtures provide near-perfect repeatability (with no human-induced holding or aiming errors). Each barrel has its own logbook to track the barrel’s usage. Interestingly, Sierra does not have a specific round count for barrel life. When a barrel starts “opening up”, i.e. showing a decline in accuracy, then the barrel is replaced, whether it has 800 rounds through it or 5,000.
Click Photo to Zoom
Sierra Bullets 10-Shot Groups at 200 yards
What kind of 200-yard accuracy can you get in an enclosed, underground test range? Would you believe 0.162 MOA at 200 yards with a .338? Check out these 10-shot test groups shot at the Sierra Test Range at 200 yards. Note that the numbers listed on each sample are actual measurements in inches. To convert to MOA, cut those numbers in half (to be more precise, divide by 2.094, which is 1 MOA at 200 yards). For example, the 0.340″ middle group works out to 0.162 MOA at 200 yards.
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Sinclair Internationalhas released an interesting article about Case Concentricity* and bullet “run-out”. This instructional article by Bob Kohl explains the reasons brass can exhibit poor concentricity, and why high bullet run-out can be detrimental to accuracy.
Concentricity, Bullet Alignment, and Accuracyby Bob Kohl
The purpose of loading your own ammo is to minimize all the variables that can affect accuracy and can be controlled with proper and conscientious handloading. Concentricity and bullet run-out are important when you’re loading for accuracy. Ideally, it’s important to strive to make each round the same as the one before it and the one after it. It’s a simple issue of uniformity.
At the request of our readers, we provide select “Deals of the Week”. Every Monday morning we offer our Bargain selections. Here are some of the best deals on firearms, hardware, reloading components, and shooting accessories. Be aware that sale prices are subject to change, and once clearance inventory is sold, it’s gone for good. You snooze you lose.
1. Natchez — Special 5 Reloading Press Kit, $199.99
This is an excellent entry-level reloading kit, which is on sale for $199.99 at Natchez Shooters Supply. We like the relatively compact Special 5 press for most reloading duties. Eventually you many want to add an additional large heavy press, but this will get the job done. This kit includes an RCBS Powder Measure, Digital Scale, Powder Trickler, Hand Priming Tool, Load Manual, Loading Tray, and more. It’s hard to beat this combination of tools for under $200.00.
2. CDNN Sports — Remington 597 for $149.99
Looking for a “first rifle” for a family member? Consider this semi-auto Remington 597. It currently retails for just $149.99. That’s right, for under $150 you can get a reliable, self-feeding rimfire rifle that will provide years of fun for a young shooter. The 597 has a stock that’s sized right for both youngsters and adults. Receivers are dovetailed for standard rimfire rings and are also drilled and tapped to allow mounting of Weaver-style bases.
3. Grafs.com — Forster Co-Ax Reloading Press on SALE
If you’ve been patiently waiting to acquire a Forster Co-Ax® reloading press, now’s the time to strike. Grafs.com has Co-Ax presses on sale this week at $289.99. That includes shipping charges (with one flat $7.95 handling charge per order).
4. Grafs.com — NEW Nikon Wind Meter for SmartPhones, $28.99
Here’s a great new gadget for under $30.00. Nikon’s new Spot On™ Ballistic Wind Meter plugs directly into the headphone port on most popular smart phones. The Spot On Wind Meter reads both wind speed and direction and inputs the data directly into Nikon’s free Spot On Ballistics Mobile App (available for iOS and Android). This allows you to quickly determine and calculate wind drift corrections without needing a separate, dedicated wind meter. When not in use, the Nikon device easily fits in a pocket.
Everyone needs a good .22 LR rimfire handgun, and the Browning Buck Mark is a classic. This stainless, bull barrel version is marked down this week to $379.99. That’s a very good price. Buckmarks, with their excellent triggers and great ergonomics, are fun to shoot and VERY accurate. This is a pistol you can keep for a life-time and pass on to your kids. Browning says: “Every Buck Mark starts out as a solid piece of aircraft-grade 7075 aluminum alloy, and then is CNC machined to exacting tolerances. The crisp single-action trigger, hand reamed chamber, target crowned barrel and finely adjustable target sights mean the Buck Mark comes ready for fun straight from the box.”
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In this video, Forum member Erik Cortina shows how to create a custom modified case for use with the Hornady Lock-N-Load Overall Length Gauge (formerly the Stoney Point Tool). While Hornady sells modified cases for many standard cartridges, if you shoot a wildcat such as the 6mm Dasher or .284 Shehane, you’ll need to create a custom modified case*. And even if you shoot a standard cartridge such as the .308 Winchester you can get more consistent measurements if you make a custom modified case from a piece of brass fired in your chamber.
The process is straight-forward. Take a piece of brass fired in your chamber and full-length size it (with about .002″ shoulder bump). Then you need to drill out the primer pocket. Erik uses a mini-lathe for the operation, but this general process can be done with a drill press or other tools. Erik shows how to do this with a 0.290″ HSS (High Speed Steel) drill bit on a mini-lathe. After drilling the hole comes the tricky part — you need to tap the case with the precise 5/16″ x 36 threads per inch (tpi) right-hand thread that matches the male thread on the O.A.L. Gauge. This 5/16″ x 36 tpi tap is pretty uncommon, but you can order it from Amazon.com if you can’t source it locally.
If you use a mini-lathe, Erik suggests loosening the tailstock slightly, so it can float while cutting the threads. Erik also says: “Make sure you get the tap on pretty tight — it’s going to want to spin.” Erik turns the case at about 100 rpm when tapping the threads. Once the case and tap are rigged, the actual tapping process (see video at 6:00) takes only a few seconds. While the mini-lathe makes the tapping process go more quickly, the threading can also be done with other systems.
TIP: Don’t just make one modified case, make three. That gives you one for your range kit, one for your home reloading bench, plus a spare (since you WILL eventually lose or misplace one).
Here’s the Stuff You Need
5/16″-36 TPI Threading Tap
The required thread is somewhat uncommon. You need a 5/16″ – 36 tpi Right Hand Thread Tap. If you can’t find it locally, Amazon.com carries the correct tap. Erik notes: “The 5/16-36 tpi tap is not a common size. I think Hornady did this on purpose to make it more difficult for the average guy to make his own modified cases.”
0.290″ Drill Bit
Erik uses an 0.290″ HSS “L” drill bit. (This “L” Letter Gauge code designates a 0.290″ diameter bit). A close metric equivalent would be 7.3 mm (0.286″). Erik says: “A 9/32″ drill will also work but it will be harder to run the tap in since the hole will be .281″ instead of .290″ with the Letter Gauge L bit.”
Tips for Using O.A.L. Gauge with Modified Case
We’ve noticed that many folks have trouble getting reliable, consistent results when they first start using the Hornady O.A.L. Gauge (formerly the Stoney Point Tool). We’ve found this is usually because they don’t seat the modified case properly and because they don’t use a gentle, consistent method of advancing the bullet until it just kisses the lands.
Here is our suggested procedure for use the O.A.L. Gauge. Following this method we can typically make three of four measurements (with the same bullet), all within .001″ to .0015″. (Yes, we always measure multiple times.)
1. Clean your chamber so there is no build-up of carbon, debris, or lube. Pay particular attention to the shoulder area.
2. Screw the modified case on to the O.A.L. Gauge. Make sure it is seated firmly (and doesn’t spin loose). Note, you may have to re-tighten the modified case after insertion in the chamber.
3. Place your selected bullet so that the ogive (max bullet diameter) is behind the case mouth. This prevents the bullet from “snagging” as you insert the tool in the action.
4. Insert the O.A.L. Gauge into your chamber smoothly. Push a little until you feel resistance. IMPORTANT — You need to ensure that the shoulder of the modified case is seated firmly against the front of your chamber. You may have to wiggle and twist the tool slightly. If you do not have the modified case seated all the way in, you will NOT get a valid measurement.
5. Advance the bullet slowly. (NOTE: This is the most important aspect for consistency!). Push the rod of the O.A.L. tool gently towards the chamber. DON’T shove it hard! Easy does it. Stop when you feel resistance.
6. IMPORTANT. After gently pushing on the rod, give the end of the rod a couple forward taps with your finger. If your bullet was slightly skewed, it may have stopped too far back. Adding a couple extra taps will fix that. If the bullet moves after the taps, then again push gently on the rod. NOT too much! You just want to push the bullet until it just “kisses” the lands and then stops. Do NOT jam the bullet into the rifling. If you do that you will never get consistent results from one measurement to the next.
* For a $15.00 fee, Hornady will make a custom modified case for you if you send two fired pieces of brass. Send fired cases and $15.00 check to: Hornady Manufacturing, Attn: Modified Cases, 108 S. Apollo St., Alda, NE 68810. More Info HERE.
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The USAMU recently published a “how-to” article about bullet sorting. While many of us may sort bullets by base-to-ogive length (and/or weight), the USAMU story explores the “how and why” of sorting bullets by Overall Length (OAL). Read the article highlights below, and make your own decision as to whether OAL sorting is worth the time and effort. Bryan Litz of Applied Ballistics says that sorting by OAL is not a bad idea, but base-to-ogive bullet sorting probably represents a better investment of your time.
Bullet Sorting by Overall Length
We’d like to share a specialized handloading technique which we’ve long found beneficial to our long-range (600 yards and beyond) accuracy. Sorting of bullets for extreme long range (LR) accuracy is not difficult to do, but some background in theory is needed.
Here at USAMU’s Handloading Shop, we only sort individual bullets for the most demanding Long-Range applications and important competitions. Only the most accurate rifles and shooters can fully exploit the benefits of this technique. The basic sorting process involves measuring the Overall Length (OAL) of the bullets, and grouping them in 0.001″ increments. It’s not unusual to find lots of match bullets that vary as much as 0.015″-0.020″ in length throughout the lot, although lots with much less variation are seen as well. Even in bullet lots with 0.015″ OAL variation, the bullet base-to-ogive length will show much less variation. Hence, our basic sort is by bullet OAL. One obvious benefit of sorting is easily seen in the attached photo. The few bullets that are VERY different from the average are culled out, reducing probable fliers.
How does one know what OAL increments to use when sorting? The answer is simple. As each lot of bullets is unique in its OAL distribution, it’s best to sample your bullet lot and see how they are distributed. In the attached photo, you will see a set of loading trays with a strip of masking tape running along the bottom. Each vertical row of holes is numbered in 0.001″ increments corresponding to the bullets’ OAL. A digital caliper makes this task much easier. As each bullet is measured, it is placed in the line of holes for its’ OAL, and gradually, a roughly bell-shaped curve begins to form.
Note that near the center, bullets are much more plentiful than near the edges. At the extreme edges, there are a few that differ markedly from the average, and these make great chronograph or sighting-in fodder. We recommend using a sample of 200 bullets from your lot, and 300 is even better. Some bullet lots are very consistent, with a tall, narrow band of highly-uniform bullets clustered together over just a few thousandths spread. Other lots will show a long, relatively flat curve (less uniform), and you may also see curves with 2 or more “spikes” separated by several 0.001″ OAL increments.
Bullet Sorting (OAL vs. Base-to-Ogive vs. Weight) — Litz Talks
I’m often asked what is a the best measure to sort bullets by, and the answer (to this and many other questions in ballistics) is: it depends.
Choosing to sort by overall length (OAL), base to ogive (BTO), bearing surface, weight, etc. can get overwhelming. Shooters typically look for something they can measure, which shows a variation and sort by that. It’s common for dimensional variations to correlate. For example, bullets which are longer in OAL are typically also shorter in BTO, and have longer noses. All these are symptoms of a bullet that was pushed a little further into the pointing die, or possibly had more than average lube while being swaged. So in essence, if you sort by BTO, you’re measuring one symptom which can indicate a pattern in the bullets shape.
So, the question still stands — what should you measure? You’ll always see more variation in OAL than BTO, so it’s easier to sort by OAL. But sometimes the bullet tips can be jagged and have small burrs which can be misleading. Measuring BTO will result in a lower spread, but is a more direct measure of bullet uniformity.
Then there’s the question of; how much variation is too much, or, how many bins should you sort into? Shooters who see 0.025” variation in BTO may choose to sort into 5 bins of 0.005”. But if you have only 0.005” variation in the box, you’ll still sort into 5 bins of 0.001”. What’s correct? You have to shoot to know. Live fire testing will answer more questions, and answer them more decisively than any amount of discussion on the subject. The test I recommend is to identify bullets on the extreme short end of the spectrum, and some on the extreme long end. Load at least 10 rounds of each, and take turns shooting 5-shot groups with them. If there is a difference, it will be evident. The results of the testing will answer your question of: should I sort based on X, Y, or Z?”
You can read more discussion on this and other similar subjects in the new Ballistics & Bullets board in the Accurateshooter.com forum. Heres a link to the thread which is discussing bullet sorting: Bullet Sorting Thread
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“The overturning moment MW tends to rotate the bullet about an axis, which goes through the CG (center of gravity) and which is perpendicular to the plane of drag….
Ruprecht Nennstiel, a forensic ballistics expert from Wiesbaden, Germany, has authored a great resource about bullet behavior in flight. Nennstiel’s comprehensive article, How Do Bullets Fly, explains all the forces which affect bullet flight including gravity, wind, gyroscopic effects, aerodynamic drag, and lift. Nennstiel even explains the rather arcane Magnus Force and Coriolis Effect which come into play at long ranges. Nennstiel’s remarkable resource contains many useful illustrations plus new experimental observations of bullets fired from small arms, both at short and at long ranges.
Shadowgraph of .308 Winchester Bullet
A convenient index is provided so you can study each particular force in sequence. Writing with clear, precise prose, Nennstiel explains each key factor that affects external ballistics. For starters, we all know that bullets spin when launched from a rifled barrel. But Nennstiel explains in greater detail how this spinning creates gyroscopic stability:
“The overturning moment MW tends to rotate the bullet about an axis, which goes through the CG (center of gravity) and which is perpendicular to the plane of drag, the plane, formed by the velocity vector ‘v’ and the longitudinal axis of the bullet. In the absence of spin, the yaw angle ‘δ’ would grow and the bullet would tumble.
If the bullet has sufficient spin, saying if it rotates fast enough about its axis of form, the gyroscopic effect takes place: the bullet’s longitudinal axis moves into the direction of the overturning moment, perpendicular to the plane of drag. This axis shift however alters the plane of drag, which then rotates about the velocity vector. This movement is called precession or slow mode oscillation.”
Raise Your Ballistic IQ
Though comprehensible to the average reader with some grounding in basic physics, Nennstiel’s work is really the equivalent of a Ph.D thesis in external ballistics. You could easily spend hours reading (and re-reading) all the primary material as well as the detailed FAQ section. But we think it’s worth plowing into How Do Bullets Fly from start to finish. We suggest you bookmark the page for future reference. You can also download the complete article for future reference and offline reading.