Our friend Gavin Gear has just released an excellent video showing how to make a threaded Modified Case for use with the Hornady Lock-N-Load Overall Length Gauge. You can watch Gavin make a Modified Case start to finish in the video below:
Video Shows How to Drill and Tap Modified Case
Gavin has some clever tricks. First he uses a sizing die to hold the cartridge case during the threading process. Second he uses two drill bits in sequence — a smaller bit to ream out the primer pocket, and then a larger “M” bit to increase the hole diameter before threading the brass. Finally he leaves the threading tap IN the brass, locks the tailstock, and then “gently pulls on the quill” to remove the brass from the die held in his lathe (See 5:46 timemark).
Get the Correct 5/16″-36 RH Tap
Unfortunately, Hornady has selected an uncommon thread type for OAL Gauges. You probably won’t be able to buy the correct 5/16″ – 36 RH HSS Tap at your local hardware store. However you CAN order this special tap from Amazon for $9.99.
Modified Case Q & A — TECH TIPS
Why do I need a Modified Case?
Every serious reloader should have a Modified Case for each cartridge type they shoot. The reason is that this allows you to get very precise measurements of the length-to-lands in your chamber. When used with the Hornady OAL Gauge, with some practice, you should be able to get repeatable length-to-lands measurements within about 0.0015″. We generally do 4-5 measurements with the OAL Gauge and usually 3 or 4 will be “on the money”. NOTE: We recommend a gentle, easy pressure on the plastic pusher rod. Don’t push too hard or you will jam the bullet hard into the lands, which produces inconsistent results.
Can’t I Just Buy a Modified Case?
Hornady makes a variety of Modified Cases sold on Amazon and through retailers such as Midsouth. While Hornady makes 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 Win, you can get more consistent measurements with a custom Modified Case.
If you do decide to make your own modified case, you’ll want to start with a case that’s been fired in your rifle. That way you get the best fit to YOUR chamber. Also, you won’t need to expand the neck to provide bullet clearance. Then you need to drill out the primer pocket and tap the base of the case to match the threads on the Hornady OAL Gauge tool. Make at least two modified cases, as you’ll probably misplace one at some point.
MORE INFORMATION: Want to learn more? We published a much longer story in which Erik Cortina explains in greater detail how to made the Modified Case. That article illustrates the 5/16″ – 36 RH HSS Tap required and shows how to set up the lathe to drill and tap your case. If you are serious about making your own Modified Cases, you should Read the Full Article.
Here’s an extreme range of .224-Caliber bullets: 35gr varmint bullet and 90gr match bullet. Of course, along with bullet length/design, you need to consider MV when choosing twist rate.
Even with the same caliber (and same bullet weight), different bullet types may require different rates of spin to stabilize properly. The bullet’s initial spin rate (RPM) is a function of the bullet’s muzzle velocity and the spin imparted by the rifling in the barrel. You want to ensure your bullet is stable throughout flight. It is better to have too much spin than too little, according to many ballistics experts, including Bryan Litz of Applied Ballistics. The late Glen Zediker put together some basic tips concerning barrel twist rates and bullet stability. These come from Glen’s book, Top Grade Ammo.
Choosing the Right Twist Rate
I’d always rather have a twist too fast than not fast enough. Generally… I recommend erring toward the faster side of a barrel twist decision. 1:8″ twist is becoming a “new standard” for .224 caliber, replacing 1:9″ in the process. The reason is that new bullets tend to be bigger rather than smaller. Don’t let a too-slow twist limit your capacity to [achieve] better long-range performance.
Base your next barrel twist rate decision on the longest, heaviest bullets you choose to use, and at the same time realize that the rate you choose will in turn limit your bullet choices. If the longest, heaviest bullet you’ll shoot (ever) is a 55-grain .224, then there’s honestly no reason not to use a 1:12″. Likewise true for .308-caliber: unless you’re going over 200-grain bullet weight, a 1:10″ will perform perfectly well.
Bullet Length is More Critical than Weight
Bullet length, not weight, [primarily] determines how much rotation is necessary for stability. Twist rate suggestions, though, are most usually given with respect to bullet weight, but that’s more of a generality for convenience’s sake, I think. The reason is that with the introduction of higher-ballistic-coefficient bullet designs, which are longer than conventional forms, it is easily possible to have two same-weight bullets that won’t both stabilize from the same twist rate.
Evidence of Instability
The tell-tale for an unstable (wobbling or tumbling) bullet is an oblong hole in the target paper, a “keyhole,” and that means the bullet contacted the target at some attitude other than nose-first.
Increasing Barrel Length Can Deliver More Velocity, But That May Still Not Provide Enough Stability if the Twist Rate Is Too Slow
Bullet speed and barrel length have an influence on bullet stability, and a higher muzzle velocity through a longer tube will bring on more effect from the twist, but it’s a little too edgy if a particular bullet stabilizes only when running maximum velocity.
My failed 90-grain .224 experiment is a good example of that: I could get them asleep in a 1:7″ twist, 25-inch barrel, which was chambered in .22 PPC, but could not get them stabilized in a 20-inch 1:7″ .223 Rem. The answer always is to get a twist that’s correct.
These tips were adapted from Glen’s popular 2016 book, Top-Grade Ammo. That work, now getting harder to find, has numerous helpful articles on technical topics. Berger Bullets also has a FREE online Twist Rate Stability Calculator, developed by Applied Ballistics.
Labor Day 2025 (September 1st) is just 5 days away. Soon we’ll be enjoying a major 3-day holiday weekend. We know many of our readers will be out on the road visiting friends or enjoying end-of-summer getaways. How do you do your reloading chores while traveling on holiday? Here’s a solution from Forum member Dave Gray (U.S. Army Retired).
Dave is a self-declared “full-time RVer” who spends most of his time on the road. Behind his Ram 3500 pickup, Dave tows a huge 41-foot Heartland Cyclone toy hauler featuring a 12X8 foot garage in the rear. In the rear garage area, which holds a compact Smart Car, Dave has set up a removable reloading bench complete with RCBS Rockchucker single stage press and Dillon progressive press.
Reloading Bench Mounts to RV Wall with Brackets
Dave explains: “I used a 2″X6″X5′ board for the bench. It’s perfect for my needs, and is easy to disassemble. I made it this small so that I can park my Smart Car in the garage during travel to my destinations. The bench, attached to the wall frames, is very solid. The presses’ centers are 3″ and 6.5″ from the brackets. [There are] four bolts on the wall into aluminum wall frame and 3 bolts in the bench. If I ever have to replace the current board, I’ll do so with oak or birch or hickory. When I’m not reloading, I remove the presses and store them in a protected space. I can easily attach other equipment to the bench by using C-Clamps.” Dave’s “rolling reloading room” looks very well thought-out. We commend Dave for his inventiveness.
How to Fill Shooting Sandbags Most Effectively
For both front and rear Edgewood bags, start by looking for the black nylon/cordura flap. This flap will have white stiches running along both sides. Note that the flap is actually two pieces of nylon/cordura which are sewn together. These two pieces must be separated at the end where there are no stitches in order to insert a funnel or other filling device.
Hold the bag so that the flap is pointed straight up and fill half way. Using a blunted rod and alternating between filling and packing, begin packing the sand firmly into the bag until the shape is uniform and you are satisfied with the firmness. Slam the base of the bag firmly on the bench several times to compact and evenly seat the sand. Then, check to see if more sand needs to be added. Repeat this process for the ears if you are filling a rear bag. Note that as the sand continues to condense during use, the bag may occasionally require additional sand until it reaches maximum capacity. NOTE: This tip is from Creedmoor Sports, which carries Edgewood Shooting Bags.
Edgewood offers an innovative rear Twisted Gater bag with an unusual asymmetrical footprint. This provides arm/hand support for the shooter while still providing superb rear support for your bench rifles.
SANDBAG Fill Options — Yes Weight Matters
For most shooting applications, “heavy is good” when it comes to sandbags. The more your sandbag weighs, the better it will resist movement or mis-alignment that can throw off a shot. In order to increase the weight of their rear bags, serious shooters have turned to exotic sand formulations that offer greater density (hence higher weight by volume) than plain silica sand (aka “play sand”).
In this article, Jason Baney reviews three popular alternatives to play sand for rear sandbags. He tested each variety to determine its density, i.e. how much volume it would displace per pound. Then he calculated how much each type of sand would weigh in various sizes of rear sandbags: standard, large, and ultra-large (Bigfoot). Check our Rapid Reference Chart to see how much weight you can add to your sandbag by switching to heavy sand.
Is heavy sand worth the added expense? For serious shooters, the answer is yes. More mass equals more stability, and a more stable bag will help you shoot tighter groups. By switching from conventional sand to Zircon or Chromite, you can DOUBLE the weight of sand in your rear bag.
Shown above are the SEB Bigfoot Bags. Note that the bags sit perfectly flat — there is no bulge on the bottom even though the bags are “packed to the brim with sand”.
Heavy Sand — Weighing the Benefits by Jason Baney
Many serious Benchrest shooters fill their sand bags with “heavy sand”. This practice may seem “overkill” to most shooters, but its benefits are realized quickly when shooting from a bench. Heavy sand is more dense than normal silica “play sand” and therefore makes the sandbag heavier and more stable. How much heavier is the heaviest sand? Check the chart below and you’ll see that Zircon sand weighs essentially TWICE as much as ordinary play sand. More weight equals more inertia opposing bag movement, plus more gravity-induced “stiction” on the bottom of the bag. In other words, using heavy sand helps your rear bag stay planted on the bench during a string of fire. When you shoot a hard-recoiling gun, the difference between a bag filled with play sand vs. Zircon is very noticeable. The Zircon-filled bag stays put. The play sand-filled bag may not.
Rapid Reference Chart
Comparative Sand Weights by Sandbag Size
SandBag Type
Play Sand
Riverbed Sand
Chromite
Zircon
Standard 5″x6″
5.1 lbs.
7.9 lbs.
9.9 lbs.
10.1 lbs.
Large 6″x8″
6.8 lbs.
10.5 lbs.
13.2 lbs.
13.4 lbs.
BigFoot 6″x13″
10.2 lbs.
15.8 lbs.
19.7 lbs.
20.1 lbs.
Weight Increase Compared to Play Sand
Zincon +98%
Chromite +94%
Riverbed Sand +55%
The Benefits of Heavier Sand
Heavy Sand helps your sandbag resist the tendency to shift or change alignment (relative to the stock) during recoil. This ability to maintain sandbag alignment is vital when shooting competitive Benchrest, either short-range or long-range. Having to fight a “migrating” rear bag during a group at 1000 yards will not do anything to help your accuracy. In non-competitive use, heavy sand can still benefit shooters. Friction from the stock on the rear bag, or bumping the bag on recoil with either a body part or pistol grip can move a lighter bag out of place and necessitate realigning the bag to get on target.
Of course there are some shooting situations where you don’t need (or don’t want) maximum sandbag weight. During a “walk-around” varmint session you may prefer a lighter bag. Beanbags that I carry around the groundhog fields stay filled with plastic beads, making the bag handier to tote. But, any rear bag used on a bench will be as heavy as I can make it while still using “sand” as filler.
Heavy Sand, Lead Shot, and Competition Rules
Some will say, “Well if you want a heavier sandbag, why not just add lead shot?” That is a great idea, but as far as I know, it is also illegal in every form of Benchrest competition. The material in sandbags must actually be “sand”, and only sand. It’s tempting to filter in a mix of shot and sand to increase weight, but that would also violate the rules.
Heavy Sand — Available Types and Properties
Heavy sand comes in several different varieties. In this article we tested three types: Zircon, Chromite, and commercial Riverbed sand (Exo-Terra brand “Reptile Sand”). All these are heavier alternatives to normal silica “play sand.” There are other types of Heavy Sand not tested here, such as Garnet Sand, which is between Chromite and Zircon in weight.
Sources: ProtektorModel.com sells black “Heavy Sand”, basically chromite. Large quantities of Zircon and Chromite are available from IFS Industries, and other industrial suppliers.
Exo-Terra Riverbed sand (amber). Available at pet stores.
Silica “Play Sand” (tan or light gray). Available at Home/Garden stores.
Zircon — Heavy-Weight Champion
To my knowledge, “Dupont Zircon M” is the heaviest “sand” that a normal human can acquire. It is also the most expensive. Zircon is a very light tan/brown color and is very similar in appearance to normal sandbox “play sand”. Zircon is normally rated as having the greatest density among heavy sands and it has the smallest particle size, though some Chromite sand density values overlap the Zircon numbers.
1.00 pound of Zircon displaces 149cc vs. 295cc for Play Sand. So, that means Zircon is 98% heavier than an equal volume of Play Sand.
CONSUMER TIP: Real ZIRCON sand is TAN in color, not black or dark gray. Some “heavy sand” vendors promise Zircon but deliver a dark gray sand that is something else entirely!
Chromite — Almost as Heavy as Zircon, and 30% Cheaper
Chromite sand is nearly the same density as Zircon but it costs quite a bit less. Chromite typically sells for about 25-30% less than Zircon (comparing bulk prices of both types of sand). Chromite sand is black in color. So when you buy “heavy sand,” make sure you are getting what you pay for.
1.00 pound of Chromite displaces 152cc vs. 295cc for Play Sand. So, that means Chromite is 94% heavier than an equal volume of Play Sand.
Riverbed Sand — Weighs Less but Costs More than Chromite
Riverbed sand, is about 30% less dense than Zircon or Chromite, but is about 150% more dense than silica sand. Depending upon where you buy this sand, and the quantity, you will most likely pay more for this sand than you would Zircon or Chromite. Riverbed sand is a conglomerate of several different sizes and colors and appears red and black. Unless you are unable to get Zircon or Chromite, I would not bother with the riverbed sand.
1.00 pound of Riverbed Sand displaces 190cc vs. 295cc for Play Sand. So, that means Riverbed Sand is 55% heavier than an equal volume of Play Sand.
Density/Volume Testing and Weight Comparisons
All four sand varieties mentioned above were tested for volumetric density by weight. Each type of sand was weighed out to 1.00 lbs. on a commercial postal scale. Each 1.00 lb sample of sand was then poured loosely into a 600ml beaker and shaken minimally to level the top surface. This served to determine the volume that the sand occupied.
1.00 pound of sand displaced the following volumes:
Zircon: 149 cc
Chromite: 152 cc
Riverbed sand: 190 cc
Play Sand: 295 cc
How do the density-volume numbers translate to the real world? Here is an estimate of how much each sand would weigh in various sizes of rear bag:
Standard Bunny Ear Bag
5″ by 6″ footprint or about 1500cc
Zircon: 10.1 lbs.
Chromite: 9.9 lbs.
Riverbed Sand: 7.9 lbs.
Play Sand: 5.1 lbs.
Protektor Doctor Bag
6″ by 8″ footprint or about 2000cc
Zircon: 13.4 lbs.
Chromite: 13.2 lbs.
Riverbed Sand: 10.5 lbs.
Play Sand: 6.8 lbs.
Seb BigFoot Rear Loaf Bag
6″ by 13″ footprint or about 3000cc
Zircon: 20.1 lbs.
Chromite: 19.7 lbs.
Riverbed Sand: 15.8 lbs.
Play Sand: 10.2 lbs.
Conclusions and Recommendations
What’s the best choice? For most users, we recommend Chromite. Chromite delivers nearly the same bag weight as Zircon but is more economical to buy. But for those who demand the maximum weight in their sandbag (without consideration of cost), Zircon is the top choice because it is sold at a finer grade (higher density) than Chromite. However, Chromite will save you money, and deliver very nearly the same amount of weight by volume. When purchased in bulk, Chromite is typically 25-30% LESS expensive than Zircon.
I would not suggest using the Riverbed sand unless you really need to fill a sandbag immediately and can’t wait to locate a source for either Zircon or Chromite. Keep in mind that Sinclair Int’l and other major mail-order vendors do sell heavy sand (though Zircon and Chromite may be much less expensive when purchased in larger quantities from local industrial sources.) The price of the Riverbed sand will vary quite a bit depending on the pet store and quantity bought. The Riverbed sand I tested, Exo-Terra Reptile sand (photo right), was fairly expensive as purchased at a pet store.
Bottom Line: When it comes time to fill your new rear bag, you may want to save a few dollars and go with cheaper Chromite sand, but if you want to gain every bit of weight possible, step up to the heavier Zircon.
Lenzi Rear bags work very well and are popular with top competitors. This are sold through PMA Tool.
The Cartridge Comparison Guide is a remarkably comprehensive 340-page, spiral-bound book. Covering over 250 cartridges, the Second Edition of the Cartridge Comparison Guide is the product of many years of labor by Andrew Chamberlain, a Utah-based hunter. Andrew says his Guide “compares every factory available cartridge from the 17 calibers up to the 50 caliber cartridges”. (Sorry, most wildcat cartridges are not covered.) Chamberlain’s Guide also compiles cartridge data from major ammunition manufacturers such as Barnes, Federal, Hornady, Norma, Nosler, Remington, Sierra, Swift, Weatherby, and Winchester. It shows the optimal velocity achieved for each bullet weight and calculates bullet energy, recoil, and powder efficiency. Large color photos illustrate handgun and rifle cartridges.
The Cartridge Comparison Guide provides data for thousands of cartridge/bullet/velocity combos. Quick reference sheets and ballistics charts cover Trajectory, Velocity, and Energy out to 500 yards. The Cartridge Comparison Guide also offers a firearms lexicon, plus Appendices covering Cartridge Selection for Game Animals, Bullet Selection/Design, Bullet Expansion, and Wound Channel Characteristics.
New Content in Second Edition of Cartridge Comparison Guide
The Cartridge Comparison Guide (Second Edition) costs $39.99 plus shipping and tax. CLICK HERE to visit the Online Store where you can order the 340-page book. Here’s what’s new in the Second Edition:
Addition of Shotgun Ammunition (Both Slug and Shot loads).
Momentum Calculation for all Rifle, Shotgun and Handgun loads.
Integration of Shotgun Slug Ammunition with Center Fire Rifle Data Tables.
Factory Load Summary Added (Shows manufacturers and loads produced).
One factory load and one hand load for every bullet weight available in each cartridge.
Over 90 pages of additional ballistics content (roughly 35% more than in First Edition).
Great Resource for Hunters
One of Chamberlain’s main goals in creating the Cartridge Comparison Guide was to help hunters select the right cartridge for the job: “This started as a personal project to gather information on the more popular cartridges commonly used for hunting. I wanted to find the best all-around performing cartridge and rifle that a guy on a budget could shoot. I began comparing cartridge performance, versatility, bullet selection, powder efficiency, recoil generation vs. energy produced, standing ballistic data for different environments….”
Giant Cartridge Poster for Computer Wallpaper (1665×1080 pixels)
Here’s a great illustration of hundreds of cartridges and shotshell types. For dedicated reloaders, this would work great as desktop “wallpaper” for your computer. CLICK HERE for full-size image.
Close-up view of a sectioned case. This one here was “fixin’ to pop”, observed Glen Zediker.
Here are highlights from an article Glen Zediker wrote for the Midsouth Blog. In that article Glen, who sadly passed away in 2020, focused on cartridge brass. Glen identified the most common failures that appear with brass that has been shot multiple times, or which has been fired at excessive pressures. Glen explained some simple ways to check your cartridge brass to detect “early warning signs” of case failure, particularly case head separation, which can be very dangerous.
How Cases Degrade with Multiple Firings By Glen Zediker
This article explains when, and then how, to check after the progress of changes commencing with the firing on a new case. It’s the “progress of degeneration,” in a way of looking at it because the concern is getting a handle on when enough change in the brass has come about to require attention. Or abandonment. As said then, for me that’s 4 firings. That, as said last time, is when I might see changes that need attention. Also as said, that figure didn’t come out of a hat, but from my own notes in running my competition NRA High Power Rifle loads. [Editor’s Note: With Lapua brass, using moderate loads, in bolt-action rifles, we typically get about 10 good (match-worthy) firings. But if you anneal your Lapua brass, and run modest pressures, Lapua brass can perform well for 20 or more load cycles.]
The areas most affected are the case neck and case head area. Case neck walls get thicker [but] the case head area body walls get thinner. Primer pockets get shallower and larger diameter.
This case shows a cracked neck AND a crack (separation) above the case head. Zediker says it is “rare to see one case with both of the most common failures. [This case] was attacked by an M14.”
Case Head — Causes of Separation and Cracking
When a case is under pressure during firing, the brass, like water, flows where it can, where it’s more free to move. Of course, the chamber steel limits the amount it can expand. The case shoulder blows fully forward and the case base is slammed back against the bolt face. There is, therefore and in effect, a tug on both ends — it gets stretched. The shoulder area is relatively free to expand to conform to the chamber, but the other end, the case head area, is not. Since that’s the area of the case with the thickest walls, it doesn’t expand “out” much at all. What it does is stretch. The “case head area,” as I refer to it here, is the portion of the case above the web, which is just above the taper that leads in to the extractor groove. The “area” extends approximately an eighth-inch up the case body.
Here’s a “pressure ring.” You’ll see this after firing, if you see it. And, if you see it, that case is done. The bright ring indicates excessive stretching, which indicates excessive thinning. If you see a ring circling the case, noticeable because it’s lighter color than the case body, and it’s in this area, I’d say that case is done. And that’s right where a “head separation” occurs. It can crack and also blow slap in two, and that’s the “separation” part of case head separation.
Photo courtesy GS Arizona.
This is a spot to keep close watch on as cases age. It is also the area that is more “protected” by sizing with less case shoulder set-back. That is, pretty much, where the freedom for the stretching movement in this area comes from (the case shoulder creates a gap). If you’re seeing a sign that a head separation [might happen with relatively few firings], chances are the shoulder set-back is excessive, and also… the load pressure level.
Bent Paper Clip Case-Wall Gauge
Editor: You can use a bent paper clip to detect potential case wall problems. Slide the paper clip inside your case to check for thin spots. GS Arizona explains: “This simple little tool (bent paper clip) will let you check the inside of cases before you reload them. The thin spot will be immediately apparent as you run the clip up the inside of the case. If you’re seeing a shiny line on the outside and the clip is really hitting a thin spot inside, it’s time to retire the case.” Photo by GS Arizona.
Monitor Primer Pocket Dimensional Changes
Another case-head-area and pressure-related check is the primer pocket. As said, the primer pocket will get larger in diameter and shallower in depth each firing. As with many such things, the questions are “when” and “how much,” and the main thing, “how much?”
If the pocket gets excessively shallow, and that’s judged by a primer that seats fully but isn’t at least a tick below flush with the case base, there could be function issues. There’s a risk of a “slam-fire” with a semi-auto that uses a floating firing pin, and, if there is actual protrusion, that has the same effect as insufficient headspace. A primer pocket uniformer can reset the depth of a shallowed primer pocket to what it should be, but the real test for me is how easily the next primer seats into it. If it’s significantly less resistance, I’ll say that case is done. Shallower can be refurbished. That’s a primary function of a primer pocket uniformer. Larger diameter, though, can’t be fixed. I’ve mentioned in another article or two that, any more at least, my main gauge of load pressure has become how much primer pocket expansion there’s been.
Many barrel-makers mark the twist rate and bore dimensions on their barrel blanks.
Does muzzle velocity change with faster or slower barrel twist rates? Absolutely, but much less than you might think. Faster twist rates do slow down bullets somewhat, but the speed loss is NOT that significant. With Bartlein .308 Win barrels of identical length and contour, a 1:12″-twist barrel was only 8 fps faster than a 1:8″-twist barrel. That was the result of testing by Applied Ballistics.
The Applied Ballistics team tested six (6) same-length/same-contour Bartlein barrels to observe how twist rate might affect muzzle velocity. This unique, multi-barrel test is featured in the book Modern Advancements in Long Range Shooting, Vol. 1. That book includes other fascinating field tests, including a comprehensive chronograph comparison.
Barrel Twist Rate vs. Velocity — What Tests Reveal by Bryan Litz
When considering barrel twist rates, it’s a common belief that faster twist rates will reduce muzzle velocity. The thinking is that the faster twist rate will resist forward motion of the bullet and slow it down. There are anecdotal accounts of this, such as when someone replaces a barrel of one brand/twist with a different brand and twist and observes a different muzzle velocity. But how do you know the twist rate is what affected muzzle velocity and not the barrel finish, or bore/groove dimensions? Did you use the same chronograph to measure velocity from both barrels? Do you really trust your chronograph?
Summary of Test Results
After all the smoke cleared, we found that muzzle velocity correlates to twist rate at the average rate of approximately 1.33 FPS per inch of twist. In other words, your velocity is reduced by about 5 FPS if you go from a 1:12″ twist to a 1:8″ twist. — Bryan Litz
Savage Test Rifle with Six Bartlein Barrels
Most shooters don’t have access to the equipment required to fully explore questions like this. These are exactly the kinds of things we examine in the book Modern Advancements in Long Range Shooting, Vol. 1. In that book, we present experiments conducted in the Applied Ballistics lab. Some of those experiments took on a “Myth Buster” tone as we sought to confirm (or deny) popular pre-conceptions. For example, here’s how we approached the question of barrel twist and muzzle velocity.
Six .308 Win Barrels from Bartlein — All Shot from the Same Rifle
We acquired six (6) barrels from the same manufacturer (Bartlein), all the same length and contour, and all chambered with the same reamer (SAAMI spec .308 Winchester). All these barrels were fitted to the same Savage Precision Target action, and fired from the same stock, and bench set-up. Common ammo was fired from all six barrels having different twist rates and rifling configurations. In this way, we’re truly able to compare what effect the actual twist rate has on muzzle velocity with a reasonable degree of confidence.
Prior to live fire testing, we explored the theoretical basis of the project, doing the physics. In this case, an energy balance is presented which predicts how much velocity you should expect to lose for a bullet that’s got a little more rotational energy from the faster twist. In the case of the .30 caliber 175 grain bullets, the math predicts a loss of 1.25 fps per inch-unit of barrel twist (e.g. a 1:8″ twist is predicted to be 1.25 fps slower than a 1:9″ twist).
Above, data shows relationship between Twist Rate and Muzzle Velocity (MV) for various barrel twist rates and rifling types. From fast to slow, the three 1:10″ twist barrels are: 5R (canted land), 5 Groove, 5 Groove left-hand twist.
We proceeded with testing all 6 barrels, with twist rates from 1:8″ to 1:12″. After all the smoke cleared, we found that muzzle velocity correlates to twist rate at the average rate of approximately 1.33 fps per inch of twist. In other words, your velocity is reduced by about 5 fps if you go from a 1:12″ twist to a 1:8″ twist. [Editor: That’s an average for all the lengths tested. The actual variance between 1:12″ and 1:8″ here was 8 FPS.] In this case the math prediction was pretty close, and we have to remember that there’s always uncertainty in the live fire results. Uncertainty is always considered in terms of what conclusions the results can actually support with confidence.
This is just a brief synopsis of a single test case. The coverage of twist rates in Modern Advancements in Long-Range Shooting Vol. 1 is more detailed, with multiple live fire tests. Results are extrapolated for other calibers and bullet weights. Needless to say, the question of “how twist rate affects muzzle velocity” is fully answered.
Other chapters in the book’s twist rate section include: · Stability and Drag — Supersonic
· Stability and Drag — Transonic
· Spin Rate Decay
· Effect of Twist rate on Precision
Other sections of the book include: Modern Rifles, Scopes, and Bullets as well as Advancements in Predictive Modeling. This book is sold through the Applied Ballistics online store at thescienceofaccuracy.com. Modern Advancements in Long Range Shooting is also available as an eBook in Amazon Kindle format.
Wind effects are complex. In trying to access wind speeds and angles, you’ll want to watch multiple indicators — mirage, dust, wind-flags, grass movement, and more. You’ll also need to be concerned about wind cycles. In the video below, Bryan Litz talks about variable wind speed along a bullet’s flight path. A respected ballistics guru, Bryan is the founder of Applied Ballistics and a designer of Berger’s Hybrid Match projectiles. He is also a past F-TR National Champion and a High Master Palma ace.
In this video, Bryan discusses how wind effects can vary in intensity at different points along the bullet’s flight path to the target. Sometimes the firing line is sheltered, and the strongest winds come into effect in the middle of the trajectory. Bryan concludes: “Wind matters everywhere … but the best thing you can do is try to get a handle on the wind [velocity and angle] where you are. That may or may not represent the wind down-range — that’s when you have to look downrange and make a judgment[.]”
Litz Competition Tip: Select your wind shooting strategy carefully. For beginners and veterans, most points are typically lost to wind. Successful shooters put a lot of thought into their approach to wind shooting. Sometimes it’s best to shoot fast and minimize the changes you’ll have to navigate. Other times it’s best to wait out a condition which may take several minutes. Develop a comfortable rest position so you have an easier time waiting when you should be waiting.
More Wind Tips from Wind Wizard Emil Praslick
In these two short videos, Emil Praslick III, former coach of the USAMU and USA National long range teams, explains how to find the wind direction and how to confirm your no-wind zero. Praslick is widely considered to be one of the best wind coaches in the USA.
When Winds Are EXTREME — Near Gale Force at Ben Avery
This video shows INSANE winds at NBRSA 100/200 Benchrest Nationals. This was filmed at the Ben Avery Range in Phoenix, AZ during the recent NBRSA 100/200 yard National Championships. Extreme to say the least. Based on what we’re seeing here, there are 20-25 mph crosswinds, with gusts to 35 mph — near Gale Force. Video by Hall-of-Fame Benchrest competitor Gene Bukys, whom we sadly lost to COVID last year. RIP Gene.
Texas gunsmith Mike Bryant reports: “This video shows the Unlimited Class 200 at the Nationals in Phoenix. I had three 10-shot groups in the low 2″ range with a 2.228″ being my big group and was glad they weren’t bigger. Thursday and Friday were the worst of the windy days. Unfortunately those were the days for the UL 200 and it was about as windy through most all of the Sporter 200.”
Excellent Wind Reading Resource
The Wind Book for Rifle Shooters covers techniques and tactics used by expert wind-readers. The authors provide a wind-reading “toolbox” for calculating wind speed, direction, deflection and drift. They explain how to read flags and mirage, record and interpret your observations, and time your shots to compensate for wind. Here are two reviews:
This is a must-have book if you are a long-range sport shooter. I compete in F-Class Open and when read it from cover to cover, it helped me understand wind reading and making accurate scope corrections. Buy this book, read it, put into practice what it tells you, you will not be disappointed. — P. Janzso
If you have one book for wind reading, this should be it. It covers how to get wind speed/direction from flags, mirage, and natural phenomenon. This is the best book for learning to read wind speed and direction. — Muddler
Many short-range Benchresters have thought about converting their 6 PPC to shoot a 30BR for score matches, or a Dasher for mid-range (or even 1000-yard) games. That way you have a rifle that does double duty, giving you the most bang for your buck. Though an action with a PPC bolt won’t normally work with 30BR/6BR/Dasher cases with their larger .308-class rim (0.4728″ diameter), there is a pretty easy solution that allows you to cycle these bigger cartridges with a 6PPC-style bolt (designed to fit .220 Russian rims).
“Rebating case rims … lets you shoot a 30BR in score matches using your PPC action. All you need is a new barrel. This saves buying another bolt, receiver, or rifle.” — Butch Lambert
Butch Lambert of ShadeTree Engineering provided this tip. Butch notes that many 6 PPC benchrest group shooters also enjoy shooting in score matches. But to be really competitive in the BR for score game, that means shooting a 30BR, which has a wider, .308-class rim (0.4728″ diameter). Likewise, if you want to compete in 600-yard registered BR events or in varmint matches, you probably want to run a bigger case, such as the 6BR, 6mm Dasher, or 6-6.5×47. Those cartridges also have the larger 0.4728″ rims.
Rebate Your 30 BR Rims
To convert a PPC-boltface action to shoot bigger cases you can spend a ton of money to buy a new bolt. That can cost hundreds of dollars. The simpler solution is to turn down the diameter of the larger cases on a lathe. Butch explains: “We’ve seen plenty of interest in rebating case rims. This lets you shoot a 30BR in score matches using your PPC action. All you need is a new barrel. This saves buying another bolt, receiver, or rifle if you have a PPC boltface. Anyone who has access to a lathe can do this job pretty easily. Yesterday I turned 150 case in about an hour.”
At right is the lathe form tool Butch uses to rebate the case rims.
As a cartridge case is reloaded multiple times, burnt powder residue and carbon builds up on the inside of the case. Unless the case interior is cleaned in some fashion, eventually you’ll see a slight reduction in case capacity. One of our Forum members from Australia wonders about the effects of reduced case capacity: “If the capacity of the case decreases as the crud builds up, then it effectively reduces the size of the cartridge (inside). Wouldn’t that change the pressure produced from that of an equivalent clean case?”
Interesting Test of Case Capacity Changes
Forum member Fred Bohl has actual test results that can help answer the above question. Fred proved that, over a 20-reload cycle, the case capacity of uncleaned cases did decline a small amount. However, surprisingly, this did not seem to affect the actual chronographed velocity of the load. Extreme Spread (ES) did increase, but Fred believes the higher ES was due to changes in case-neck tension, rather than due to the slight reduction in case capacity. Fred reports:
“Back when beginning to use ultrasonic case cleaning, part of the motivation was to get the inside clean based on the assumption that allowing burnt residue to build up inside cases would affect capacity, and, ultimately, performance. An experiment was done to test this hypothesis. The load used, 30.5 grains of RL15 behind 107gr SMKs in a 6mmBR, was selected for best group and lowest ES in prior load development. It turned out to be 92% of initial case capacity and neither “full” or compressed. (I would suspect that different powders, load weight, and total case capacity might produce very different results.)
We took 30 cases of identical initial capacity and tracked three lots of 10 each:
LOT 1: No Internal cleaning LOT 2: Cleaned with media in tumbler LOT 3: Cleaned with Ultrasound machine
Each case (in each lot) was shot and reloaded 20 times. The simplified results after 20 reloads of each lot were as follows:
Lot 1 (not cleaned) – 0.3 to 0.4 gr. loss of capacity, 5 to 8 fps greater ES.
Lot 2 (tumble cleaned) – 0.1 to 0.3 gr. loss of capacity, 4 to 6 fps greater ES.
Lot 3 (ultrasonic cleaned) – no loss of capacity, no detectable change in ES.
FINDINGS
There was no detectable correlation of velocity change to the lots. An oddity was that on very hot days Lot 1 velocities were, occasionally, slightly higher. From results of another ongoing test, I believe the above differences in ES are probably due more to variance in bullet grip tension than case capacity. The ultrasound cleaned cases (LOT 3) did maintain the lowest ES, but we are not 100% sure of the reasons why. More consistent bullet seating might be the reason.”
Editor’s NOTE: Fred’s results do suggest that carbon build-up inside the uncleaned cases might cause a slight increase in pressure that shows up on hot days. Fred has posted that: “A local shooter reported doing the 20 reload, no-clean test on a .308 that gave a loss of capacity of 2.0 grains, doubled ES and significant velocity changes. However, I don’t have any details on his load weight or powder.” Obviously a lot of carbon can build up with 20 reloads. Many shooters retire their brass before then.
Ultrasonic Cleaning and Neck Lube
Some time ago, Jason Baney did a lengthy test on ultrasonic cleaning. Jason found that with his ultrasonically-cleaned cases, the inside of the necks got so “squeaky clean” that he needed to use dry lube in the necks. Jason uses the $21.50 dry lube kit from Neconos.com. This applies ultra-fine Moly powder to the neck using small carbon steel balls.
Increasing Barrel Length Can Deliver More Velocity, But That May Still Not Provide Enough Stability if the Twist Rate Is Too Slow
Labor Day 2025 (September 1st) is just 5 days away. Soon we’ll be enjoying a major 3-day holiday weekend. We know many of our readers will be out on the road visiting friends or enjoying end-of-summer getaways. How do you do your reloading chores while traveling on holiday? Here’s a solution from Forum member Dave Gray (U.S. Army Retired).
Reloading Bench Mounts to RV Wall with Brackets
How to Fill Shooting Sandbags Most Effectively
For most shooting applications, “heavy is good” when it comes to sandbags. The more your sandbag weighs, the better it will resist movement or mis-alignment that can throw off a shot. In order to increase the weight of their rear bags, serious shooters have turned to exotic sand formulations that offer greater density (hence higher weight by volume) than plain silica sand (aka “play sand”).
Many serious Benchrest shooters fill their sand bags with “heavy sand”. This practice may seem “overkill” to most shooters, but its benefits are realized quickly when shooting from a bench. Heavy sand is more dense than normal silica “play sand” and therefore makes the sandbag heavier and more stable. How much heavier is the heaviest sand? Check the chart below and you’ll see that Zircon sand weighs essentially TWICE as much as ordinary play sand. More weight equals more inertia opposing bag movement, plus more gravity-induced “stiction” on the bottom of the bag. In other words, using heavy sand helps your rear bag stay planted on the bench during a string of fire. When you shoot a hard-recoiling gun, the difference between a bag filled with play sand vs. Zircon is very noticeable. The Zircon-filled bag stays put. The play sand-filled bag may not.
Dupont Zircon M (pale tan): 165-175 lb/cu.ft; avg. particle size 0.01″.
Prince Minerals Chrome CAST 7850 (Chromite) (black): 172 lb/cu.ft; avg. particle size 0.02″.
Zircon — Heavy-Weight Champion
Chromite — Almost as Heavy as Zircon, and 30% Cheaper
Riverbed Sand — Weighs Less but Costs More than Chromite
I would not suggest using the Riverbed sand unless you really need to fill a sandbag immediately and can’t wait to locate a source for either Zircon or Chromite. Keep in mind that 
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