The Tactical Rifle Shooters Facebook Group recently showcased tools used to measure case headspace before and after “bumping” the shoulder. After a case is fired, hand-loaders who full-length size their cases will typically bump the shoulders back anywhere from .001″ to .0035″, depending on the rifle and application. With our 6mmBR and Dasher cases we like about .0015″ bump.
You want the amount of case sizing and bump to be the same for all your brass. To ensure uniformity, it makes sense to measure your cases before and after the FL sizing process. When we have time, we check every case. Other folks will simply check the first 3-4 cases coming out of the FL sizing die to ensure the FL die setting is correct and delivering desired headspace/bump.
1. Whidden Gunworks Shoulder Bump Gauge
There are a variety of tools that can be used to measure shoulder bump. Our favorite is a special cartridge-specific bushing made by Whidden Gunworks. The Whidden Shoulder Bump Gauge enables you to adjust your sizing die to the desired measurement. The bump gauge is attached to your calipers with a set screw and determines the measurement from the base to the shoulder of the case. The photo below, from Tactical Rifle Shooters, shows the Whidden Bump Gauge for the .375 CheyTac cartridge.
2. Dave Manson Vertical Comparator with Dial Read-Out
Dave Manson states: “This tool was designed to make life easier for the advanced shooter and re-loader by allowing precise measurement of ammunition, case, and chamber headspace. With this information, the re-loader will be able to fine-tune clearances and fits between his ammunition and chamber, with resultant improvements in accuracy and case life.” The functions of the Manson Comparator are:
1. Measure headspace of factory or reloaded ammunition
2. Quantify chamber headspace by measuring headspace of a fired case
3. Ensure minimal shoulder set-back when setting up re-loading dies
4. Compare base-to-ogive length to ensure consistent bullet-to-rifling relationship.
Hornady’s Lock-N-Load Headspace Comparator system is easy-to-use and handy. You can get a kit with Red bushing-holder body and 5 bushings for $39.99 at Midsouth. Hornady explains: “The Lock-N-Load® Headspace Comparator… gauge measures variations in brass before and after firing or re-sizing. It allows for headspace comparison between fire-formed brass and re-sized brass.” IMPORTANT: Hornady states: “To determine the proper bushing diameter for your cartridge, simply add the neck diameter and the shoulder diameter and divide that number by two. Use the bushing closest to that number.” Hornady offers five: .330″, .350″, .375″, .400″, and .420″.
One tip — We have found the Hornady gauges may vary a little from unit to unit even with the same nominal size. If you have more than one gauge for the same cartridge, test each on your brass — you may then note a slight difference in your bump measurements. Mark one and use that consistently. There is also an Anvil Base Kit that mounts to the opposite blade on the caliper. This provides a more stable surface for the base of your case.
4. L.E. Wilson Case Gage Depth Micrometer
If you are looking for precise “bump” measurements without having to mess with calipers and clamp-on gauge blocks, you may want to consider the L.E. Wilson Case Gage Depth Micrometer (currently $130.00). This takes very precise, repeatable measurements, but you need to know your starting point. The manufacturer explains: “Every reloader should know exactly how much your Full Length Sizing Die is pushing back the shoulder. With the NEW Case Gage Depth Micrometer you can do just that! It has never been easier to measure you cases headspace before and after sizing. The Depth Mic allows you to slip the micrometer perfectly over the top of the Gage with your case inserted into the Gage and take a measurement. Micrometer has graduations of .001″. The Case Gage Depth Micrometer is set to a zero of .100″ on the scale at our factory. Because of differences in ‘feel’ and temperature, we include a the Gage Block for you to test Zero and to adjust if necessary.”
5. Pistol Brass Case DIY Bump Gauge
Last is a “field expedient” set-up if you do not have any of the comparator tools shown above. A sized .45 ACP case (or other suitable pistol case) can be used to measure shoulder bump. The mouth of the pistol case sits on the shoulder of your rifle cartridge brass.
Make sure the .45 ACP case is trimmed square and that it is round. We recommend you first run it through an expander, then size it, trim it and chamfer. Next, take the .45 ACP case and slip it over the neck of a fired, unsized rifle case with the primer removed. Align the two cases between the jaws of your calipers and note the length from rim to rim (See left photo below).
OK, now you have the length for a fired rifle case BEFORE sizing. Next, take a full-length sized rifle case (without primer) and do the same thing, placing the .45 ACP case over the neck of the FL-sized case (Right Photo). The difference between the two numbers is the amount of “bump” or set-back you are applying to the shoulder. Here the difference is .0015″. The amount of bump you need varies with your chamber and your load, but .0015-.002″ is a good initial setting.
SSG Greg Markowski of the USAMU at Camp Perry, Ohio.*
The U.S. Army Marksmanship Unit (USAMU) fields pistol teams as well as rifle and shotgun competition squads. Consequently the USAMU’s Reloading Shop loads tens of thousands of pistol rounds every year. In this article, the USAMU’s handgun experts talk about reloading for handguns — with smart tips on how to achieve superior accuracy with 100% reliability. This article, which offers important insights on COAL, primers, crimps and more.
This video shows .45 ACP centerfire pistol competitors at Camp Perry
Precision Pistol Reloading — Recommended Methods
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 [at 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!
TOP IMAGE: SSG Greg Markowski, a shooter/instructor with the USAMU, fires his pistol during the 2018 Civilian Marksmanship Program’s National Pistol Matches at Camp Perry, Ohio. At that event, Markowski claimed the General Mellon Trophy, General Patton Trophy and the General Custer Trophy. U.S. Army photo by Maj. Michelle Lunato/released by Defense Visual Information Distribution Service.
Photo 1: Three Near-Equal-Weight 7mm Bullets with Different Shapes
TECH TIP: Bullets of the same weight (and caliber) can generate very different pressure levels due to variances in Bearing Surface Length (BSL).
This article, from the USAMU Facebook Page, concerns reloading safety. In the relentless quest for more speed and flatter ballistics, some hand-loaders load way too hot, running charges that exceed safe pressure levels. Hint: If you need a mallet to open your bolt, chances are your load is too hot. Stay within safe margins — your equipment will last longer, and you won’t risk an injury caused by over-pressure. In this article, the USAMU explains that you need to account for bullet shape, diameter, and bearing surface when working up a load. Don’t assume that a load which is safe for one bullet will be safe for another even if both bullets are exactly the same weight.
How Bullet Profile and Bearing Surface Affect Pressure Levels
Today, we continue our handloading safety theme, focusing on not inadvertently exceeding the boundaries of known, safe data. Bullet manufacturers’ loading manuals often display three, four, or more similar-weight bullets grouped together with one set of load recipes. The manufacturer has tested these bullets and developed safe data for that group. However, seeing data in this format can tempt loaders — especially new ones — to think that ALL bullets of a given weight and caliber can interchangeably use the same load data. Actually, not so much.
However, bullet designs include many variables such as different bearing surface lengths, hardness, and even slight variations in diameter. In fact, diameters can occasionally range up to 0.001″ by design. Thus, choosing untested bullets of the same weight and caliber, and using them with data not developed for them can yield excess pressures.
This is only one of the countless reasons not to begin at or very near the highest pressure loads during load development. Always begin at the starting load and look for pressure signs as one increases powder charges.
Bullet Bearing Surface and Pressure
Bullet bearing surface length (BSL) is often overlooked when considering maximum safe powder charges and pressures. In Photo 1, note the differences in the bullets’ appearance. All three are 7 mm, and their maximum weight difference is just five grains. Yet, the traditional round nose, flat base design on the left appears to have much more BSL than the sleeker match bullets. All things being equal, based on appearance, the RN/FB bullet seems likely to reach maximum pressure with significantly less powder than the other two designs.
TECH TIP: Bullets of the same weight (and caliber) can generate very different pressure levels due to variances in Bearing Surface Length (BSL).
Bullet 1 (L-R), the RN/FB, has a very slight taper and only reaches its full diameter (0.284 inch) very near the cannelure. This taper is often seen on similar bullets; it helps reduce pressures with good accuracy. The calculated BSL of Bullet 1 was ~0.324″. The BSL of Bullet 2, in the center, was ~0.430″, and Bullet 3’s was ~ 0.463″. Obviously, bullets can be visually deceiving as to BSL!
Some might be tempted to use a bullet ogive comparator (or two) to measure bullets’ true BSL for comparison’s sake. Unfortunately, comparators don’t typically measure maximum bullet diameter and this approach can be deluding.
Note: Due to time constraints, the writer used an approximate, direct measurement approach to assess the bullets’ different BSLs. While fairly repeatable, the results were far from ballistics engineer-grade. Still, they are adequate for this example.
Photo 2: The Perils of Measuring Bearing Surface Length with Comparators
In Photo 2, two 7mm comparators have been installed on a dial caliper in an attempt to measure BSL. Using this approach, the BSLs differed sharply from the original [measurements]. The comparator-measured Bullet 1 BSL was 0.694” vs. 0.324” (original), Bullet 2 was 0.601” (comparator) vs. 0.430” (original), and Bullet 3 (shown in Photo 2) was 0.602” (comparator) vs. 0.463” (original). [Editor’s comment — Note the very large difference for Bullet 1, masking the fact that the true full diameter on this bullet starts very far back. You can use comparators on calipers, but be aware that this method may give you deceptive reading — we’ve seen variances just by reversing the comparators on the calipers, because the comparators, typically, are not perfectly round, nor are they machined to precision tolerances.]
Thanks to the U.S. Army Marksmanship Unit for allowing the reprint of this article.
If you asked a group of shooters to explain the difference between CUP and PSI, the majority would probably not be able to give a precise answer. But, for safety reasons, it’s very important that all hand-loaders understand these important terms and how they express cartridge pressures.
The ANSI / SAAMI group, short for “American National Standard Institute” and “Sporting Arms and Ammunition Manufacturers’ Institute”, have made available some time back the voluntary industry performance standards for pressure and velocity of centerfire rifle sporting ammunition for the use of commercial manufacturers. [These standards for] individual cartridges [include] the velocity on the basis of the nominal mean velocity from each, the maximum average pressure (MAP) for each, and cartridge and chamber drawings with dimensions included. The cartridge drawings can be seen by searching the internet and using the phrase ‘308 SAAMI’ will get you the .308 Winchester in PDF form. What I really wanted to discuss today was the differences between the two accepted methods of obtaining pressure listings. The Pounds per Square Inch (PSI) and the older Copper Units of Pressure (CUP) version can both be found in the PDF pamphlet.
CUP Pressure Measurement
The CUP system uses a copper crush cylinder which is compressed by a piston fitted to a piston hole into the chamber of the test barrel. Pressure generated by the burning propellant causes the piston to move and compress the copper cylinder. This will give it a specific measurable size that can be compared to a set standard. At right is a photo of a case that was used in this method and you can see the ring left by the piston hole.
PSI Pressure Measurement
What the book lists as the preferred method is the PSI (pounds per square inch or, more accurately, pound-force per square inch) version using a piezoelectric transducer system with the transducer flush mounted in the chamber of the test barrel. Pressure developed by the burning propellant pushes on the transducer through the case wall causing it to deflect and make a measurable electric charge.
Q: Is there a standardized correlation or mathematical conversion ratio between CUP and PSI values?
Mahin: As far as I can tell (and anyone else can tell me) … there is no [standard conversion ratio or] correlation between them. An example of this is the .223 Remington cartridge that lists a MAP of 52,000 CUP / 55,000 PSI but a .308 Winchester lists a 52,000 CUP / 62,000 PSI and a 30-30 lists a 38,000 CUP / 42,000 PSI. It leaves me scratching my head also but it is what it is. The two different methods will show up in listed powder data[.]
So the question on most of your minds is what does my favorite pet load give for pressure? The truth is the only way to know for sure is to get the specialized equipment and test your own components but this is going to be way out of reach for the average shooter, myself included. The reality is that as long as you are using printed data and working up from a safe start load within it, you should be under the listed MAP and have no reason for concern. Being specific in your components and going to the load data representing the bullet from a specific cartridge will help get you safe accuracy. [With a .308 Winchester] if you are to use the 1% rule and work up [from a starting load] in 0.4 grain increments, you should be able to find an accuracy load that will suit your needs without seeing pressure signs doing it. This is a key to component longevity and is the same thing we advise [via our customer service lines] every day. Till next time, be safe and enjoy your shooting.
Hodgdon Powder Company (Hodgdon) offers a series of professionally-produced, “how-to” instructional videos on its online Reloading Data Center. These 3.5-minute videos present rifle, pistol, and shotshell reloading basics in an easy-to-understand, step-by-step format. These mobile-friendly, informative videos can also be viewed on a smart phone or tablet.
Along with these videos, you’ll find a ton of useful information on Hodgdon’s updated Reloading Data Center at hodgdon.com. From the landing page choose rifle, pistol, shotgun, or muzzle-loader, and then click “Get Details”. This will launch a page where you can find loads by selecting Cartridge, Bullet Weight, Powder Maker, and Powder Type (such as Varget or H4350).
Click to Watch Hodgdon Rifle Reloading Video:
Click to Watch Hodgdon Pistol Reloading Video:
In addition to these videos, Hodgdon’s Reloading Data Center (RDC) provides a wealth of information on Hodgdon®, IMR®, Accurate, Ramshot®, and Winchester® propellants. Along with reliable load data, you’ll find explanations of reloading basics, safety procedures, plus answers to frequently asked questions (FAQ).
Creedmoor Sports has recently expanded and updated the Creedmoor Sports InfoZone. This web resource contains valuable information about reloading, rifle maintenance, marksmanship skills, and gunsmithing. In addition, the InfoZone has Competition Reports, numerous Gear Reviews, and general Shooting Sports News.
For this Saturday Showcase, you’ll find five InfoZone Videos hosted by Bill Gravatt, President of Creedmoor Sports. There are over 85 other videos on the Creedmoor Sports YouTube Channel. Bill Gravatt is an expert on reloading processes and gear. He developed many of the popular tools for Sinclair Int’l, and now he directs operations for Creedmoor Sports.
Reloading Procedures with Bill Gravatt
Here are five helpful videos Bill Gravatt created for the Creedmoor Sports InfoZone. These videos cover a variety of essential processes for handloading. In addition Bill Shows how to find the exact twist rate in your rifle barrels.
How to Determine a Barrel Twist Rate
Bill Gravatt of Creedmoor Sports demonstrates an easy method to determine your barrel’s twist rate. Knowing the twist rate is essential to selecting suitable bullets for your discipline.
How to Seat Bullets with Inline Press
Many top Benchrest and F-Class shooters favor inline presses for bullet seating. With good hand dies (such as Wilson) and a inline Arbor press (such as a 21st Century), you can get great results with super seating depth consistency and very low run-out.
How to Trim Cases with L.E. Wilson Trimmer
There are many ways to trim cartridge brass. If you need to trim hundreds of cases it may pay to have a dedicated power trimmer. However, for most rifle shooters, a good hand trimmer will do the job very well. We regularly use a Wilson trimmer to trim our cases, as demonstrated in this video.
How to Clean Cartridge Cases
It is important to regularly clean cartridge brass. There are many different means. Wiping the outside with a solvent is a good start. For more thorough cleaning inside and out tumbling or wet-tumbling will do the job. After tumbling in media, you should always check the primer pockets and flash holes before loading.
How to Clean Reloading Dies
Cleaning your reloading dies is something that many who reload often neglect. In this 60-second Tech Tip, Bill Gravatt provides some tips on cleaning your reloading dies.
BONUS Video: How to Fine Tune Seating Depth
Now that you’ve learned Reloading Basics from the Creedmoor Sports videos, here’s a great video from our friend Keith Glasscock that will help you get optimal results when seating bullets. Keith is one of America’s greatest F-Class competitors, with multiple podium finishes at F-Class National Championships. With over 213,000 views, this is the most popular video Keith has created for his Winning in the Wind YouTube Channel.
About Creedmoor Sports — 45 Years of Service to Marksmen
For the past 45 years, since 1979, Creedmoor Sports has been supplying quality equipment and supplies to avid shooters in a wide variety of disciplines: Rimfire, F-Class, PRS/NRL, Silhouette, Service Rifle, Benchrest, and more. Specializing in competitive centerfire, smallbore, and air rifle accessories, as well as reloading components and tools, Creedmoor Sports seeks to provide its customers with the right gear to help them achieve their personal shooting goals.
From time to time, we all encounter a primer that doesn’t go off. It’s normal to attribute the problem to a bad primer. But sometimes there are other explanations. George S., one of our Forum members, experienced a couple failures to fire, but he learned that the issue was his priming TOOL, not his primers. Here’s what George told us. There’s a lesson to be learned:
“I had issues with CCI 450s when I had my first 6BR barreled. I had probably three or four out of 20 rounds that failed to fire. the primers were dented but didn’t fire. I called CCI since I had bought a case of them. The tech was decent enough but had the audacity to tell me I was not seating the primers all the way in the pocket. I proceeded to let him know I had been reloading longer than he had been alive and I knew how to seat a primer.
Turns out that I did and I didn’t! I was using the RCBS primer tool I had used for years and the primers felt just fine to me. I finally decided to check the tool and since I had a new one I took the seating pins out and measured them. The seating pin on the tool I had been using for years was shorter by a few thousandths! I then used the pin from the new primer tool and darned if the primers that didn’t seat down to the bottom of the cup.
I switched to a K&M primer tool for seating the CCI primers and have not had a problem since. It was the combination of harder cup and lack of proper seating. I did call the CCI tech back and apologized for being an idiot.”
Another Forum member witnessed a problem cause by misuse of a priming tool: “I did … see a failure to fire on a Rem 9 1/2 primer only a week ago. That was in the new Rem muzzleloader that uses a primed case to ignite the pellets. After watching the muzzleloader’s owner seat his primers, I believe that it was operator error not the primer. He was seating the primer and then squeezing the priming tool so hard that his hands hurt after a few. We got that corrected.”
In the ELR game, particularly the King of 2 Miles (KO2M), it’s “go big or go home”. The top shooters run large-capacity cartridges that push large-caliber, ultra-high BC bullets at very high velocities. Bullets launched by cartridges such as the .416 Barrett can sustain supersonic velocities at Extreme Long Ranges — and that’s what it takes to win. The .416 Barrett can launch a 550-grain solid bullet at 3000+ FPS.
Photo from ELR Competitor Corbin Shell.
2018 and 2019 Kings of 2 Miles Loaded on RCBS Presses
So how do you load jumbo cartridges such as the .416 Barrett? It takes a big, heavy, super-strong reloading press. We’ve learned that two recent King of 2 Miles champions, Paul Phillips (2019) and Robert Brantley (2018) both loaded their KO2M ammo on RCBS AmmoMaster .50 BMG presses. Phillips loaded .416 Barrett ammo, while Brantley loaded a similar .416 MCS cartridge.
In 2018, Robert Brantley topped the field using his custom .416 MCS cartridge. Then in 2019, Paul Phillips won the K02M competition shooting a .416 Barrett, with Brantley a close second. Both Phillips and Brantley use the RCBS AmmoMaster .50 BMG single stage press kit and RCBS .416 Barrett dies to hand-load for extreme long-range. “My ammo has been much more consistent after switching to the RCBS press and dies,” remarked Phillips, who runs the Global Precision Group. Brantley said he uses RCBS products for most of his reloading needs — from the dies and AmmoMaster, to the ChargeMaster and Brass Boss. His custom .416 MCS loads launch a 550-grain bullet more than 3,100 fps.
Loading with RCBS AmmoMaster .50 BMG Press
This video shows reloading with the RCBS AmmoMaster .50 BMG press. While this video shows .50 BMG cases being loaded, the principles are the same for loading the .416 Barrett cartridge or other big rounds. Big cases need big presses!
Here’s an inexpensive procedure that can help you load straighter ammo, with slightly better measured concentricity (i.e. less run-out) on the case necks and bullets. Simply use a Rubber O-Ring on the underside of the die locking ring. This allows the die to self-align itself (slightly) to the case that is being sized. Without the O-Ring, if the flat surface on the top of your press is not perfectly square with the thread axis, your die can end up slightly off-angle. This happens when the bottom of the locking ring butts up tight against the top of the press. The O-Ring allows the die to float slightly, and that may, in turn, reduce the amount of run-out induced during case sizing.
Top prone shooter GSArizona, who sadly passed last year, tried this trick and said it works: “Go to your local hardware store and get a #17 O-Ring (that’s the designation at Ace Hardware, don’t know if its universal). Slip the O-Ring on the die and re-adjust the lock ring so that the O-Ring is slightly compressed when the die is at the correct height. Size and measure a few more cases. You will probably see a slight improvement in neck concentricity as the die can now float a bit as the case enters and leaves it. This isn’t going to be a dramatic improvement, but it’s a positive one.”
We want to stress that adding O-Rings to sizing dies may help some reloaders, but we don’t offer this as a panacea. Try it — if using the O-Ring reduces measured runout that’s great. If it doesn’t, you’ve only spent a few pennies to experiment.
Lee Precision makes die lock rings with built-in O-Rings. Lee’s distinctive lock ring design allows the same kind of self-alignment, which is good. However, Lee lock rings don’t clamp in place on the die threads, so they can move when you insert or remove the dies — and that can throw off your die setting slightly. By using an O-Ring under a conventional die lock ring (that can be locked in place), you get the advantages of the Lee design, without the risk of the lock ring moving.
The USAMU has 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
Expert advice from Bryan Litz, Applied Ballistics
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 discussions on this and other similar subjects in our Accurateshooter.com Shooters’ Forum. Here’s a link to a thread discussing bullet sorting: Bullet Sorting Thread
Use Consistent Brass
Bullet 1 (L-R), the RN/FB, has a very slight taper and only reaches its full diameter (0.284 inch) very near the cannelure. This taper is often seen on similar bullets; it helps reduce pressures with good accuracy. The calculated BSL of Bullet 1 was ~0.324″. The BSL of Bullet 2, in the center, was ~0.430″, and Bullet 3’s was ~ 0.463″. Obviously, bullets can be visually deceiving as to BSL!
CUP Pressure Measurement
