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.
Guys — honestly, if you do anything today on this site, watch this video. You won’t be disappointed. Guaranteed. This is a very informative (and surprisingly entertaining) video. Every serious hand-loader should watch this video to see how cartridge cases are made. Your Editor has watched the video 5 times now and I still find it fascinating. The camera work and editing are excellent — there are many close-ups revealing key processes such as annealing and head-stamping.
VERY Informative Video Show Cartridge Brass and Ammunition Production:
Norma has released a fascinating video showing how bullet, brass, and ammunition are produced at the Norma Precision AB factory which first opened in 1902. You can see how cartridges are made starting with brass disks, then formed into shape through a series of processes, including “hitting [the cup] with a 30-ton hammer”. After annealing (shown at 0:08″), samples from every batch of brass are analyzed (at multiple points along the case length) to check metal grain structure and hardness. Before packing, each case is visually inspected by a human being (3:27″ time-mark).
The video also shows how bullets are made from jackets and lead cores. Finally, you can watch the loading machines that fill cases with powder, seat the bullets, and then transport the loaded rounds to the packing system. In his enthusiasm, the reporter/narrator does sometimes confuse the term “bullets” and “rounds” (5:00″), but you can figure out what he means. We definitely recommend watching this video. It’s fascinating to see 110-year-old sorting devices on the assembly line right next to state-of-the art, digitally-controlled production machinery.
Video tip by EdLongrange. We welcome reader submissions.
At the request of our readers, we provide select “Deals of the Week”. Every Sunday afternoon or Monday morning we offer our Best Bargain selections. Here are some of the best deals on firearms, hardware, reloading components, optics, 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.
NOTE: All listed products are for sale to persons 18 years of age or older. No products are intended for use by minors.
1. Graf & Sons — Forster CO-AX Reloading Press, $334.79
⏺️ » Excellent versatile press with good discount
The Forster Co-Ax Reloading Press is one of our favorite presses. With an open front, the Co-Ax features dual floating guide rods. These provide perfect alignment of the die and the case because the shell holder jaws float with the die, thereby permitting the case to center precisely in the die. And as the die slides in a slot with the lock ring (rather than screwing down in a threaded hole), it is fast and easy to change dies. Right now you can save $37 with this Grafs.com sale.
2. MidwayUSA — Major Brands Optics Sale, Huge Discounts
⏺️ » Save on great scopes from Zeiss, Vortex, Leupold, SIG Sauer, Burris
⏺️ » Save big bucks on major-brand target and hunting bullets
Need bullets? Check out Midsouth’s Bulk Bullets Sale. A major U.S. bullet-maker made these poly-tipped bullets for Midsouth using proven designs for hunting, varmint, and target applications. The varmint bullets’ thin jackets allow for rapid expansion, even at lower velocities. These bullets are packaged into polymer bags. That reduces the price by eliminating factory packaging. NOTE: Buyer reports are very positive.
4. Amazon — Derraco PCPS Priming Tool, $199.95
⏺️ » Innovative precision priming tool mounts to press
Turn your standard single-stage reloading press into a precision priming system with the Derraco PCPS Precision Priming die/Primer Seating Tool (#ad). This advanced tool is compatible with any reloading press that accommodates 7/8-14 reloading dies and standard T-shaped shell holders. For a wide variety of single-stage presses, this unique precision priming tool will consistently deliver high-precision results thanks to the precision adjuster and micrometer hard stop.
⏺️ » Good quality, large, rugged rifle case at attractive price
When flying or driving it’s vital to protect your rifles. A good hard case option (at a great price) is the APACHE 9800 Weatherproof Protective Rifle Case. On sale for $149.99, this 53″-long case is $190.00 less than an equivalent-size Pelican case. Constructed from durable polypropylene, this quality hard case can protect long guns from from impact, moisture, and dust. The built-in purge valve equalizes pressure so you can open the case after changing elevations. NOTE: Case interior dimensions are 50⅜” by 13⅝”.
⏺️ » Excellent tool for fast, reliable base-to-ogive measurement
When loading precision ammo, you need to accurately measure the base-to-ogive of loaded rounds. A good tool for this task is the Hornady Lock-N-Load Comparator Kit. This can measure seating depth of loaded ammunition quickly and precisely. Attached to calipers, this measures from the cartridge base to the bullet ogive, ensuring consistent seating. This basic set includes the comparator body, plus 7 inserts covering .224, .243 (6mm), .257, .264, .277, .284 (7mm) and .308 bullet diameters.
⏺️ » Great transport case holds 5 handguns plus magazines.
If you often transport multiple pistols, this is a great travel case. The LOTOCASE TSA-Approved Handgun Case holds 5 handguns, plus 16 magazines and features a rechargeable, moisture-absorbing silica gel canister to prevent gun rust. Well-designed with slots for pistols and mags, this rugged hard case is a good option for handgun competitors. NOTE: For long-term storage, put your handguns in anti-rust fabric sleeves and store in a good gun safe.
8. Amazon — Coobeast 38pcs Digital Torque Screwdriver, $59.98
⏺️ » Advanced, modern tool measures proper torque
Setting proper torque on rings, actions and more is critical to precision shooting. For precise torqueing jobs, we like the Coobeast 38pcs Digital Torque Screwdriver. With a power drive with digital display (and certified calibration), this electric torque screwdriver offers precise torques. The drivers are made of hardened chrome vanadium steel.
9. Midsouth — Primer Sale w/ CCI, Federal, Rem, Magtech & more
⏺️ » Large supply of magnum, large, and small primers at good prices
Over the last few years premium brand primers have been pricey and hard to source. Thankfully, things are getting much better. And right now Midsouth is running a major Midsouth Primer Sale with significant savings on CCI, Federal, Winchester, Magtech and other brand primers. Yes there are large rifle primers along with hard-to-find Federal 205M small rifle primers — popular with competitive shooters. Both 1000ct and 5000ct packages are on sale.
10. Amazon — 52″ Rifle Soft Case, $21.98
⏺️ » Very low price for handy case for long-barrel rifles
Sometimes you just need a simple, basic gun case for taking your rifles to the range in your vehicle. This 52″ Soft Rifle Case can handle those duties and is big enough for competition F-Class and Full-bore rifles. This gun case has decent padding, a water-resistant nylon shell (green, tan, or black), and comes with a handy adjustable shoulder strap. Choose either 52″ case for $21.98 or 42″ version for $19.99.
11. Amazon — Frankford Arsenal Digital Caliper, $37.19
⏺️ » Good features and measures both inches (SAE) and millimeters
Accurate measurement of cartridges and components is critical for precision reloading. All hand-loaders should have a good set of digital calipers. These Frankford Arsenal calipers are accurate to within .001” when measuring case length, neck and base diameters, overall length. These calipers also can show both SAE (inch) and Metric (mm) measurements.
As an Amazon affiliate, this site can earn revenues through sales commissions.
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.
Tech Report by Brian Williams
Reloading for a military surplus gun is different than loading for a modern precision rifle in my opinion. There are a few tasks that carry over from one to the other, but the main goal is slightly different. The target shot in the CMP games matches has a rather generous 10 ring, and with a little larger target your focus needs to change from a round with ultra accuracy to a round that is safe and functions well in your particular rifle.
Reloading for Vintage .30-06 Springfield Rifles
Bullet Selection — With the .30-06 for my Garands and Springfields I stick mostly with 168gr bullets plus some 155-grainers. These bullet weights have just worked for me in the past.
Cartridge Brass (Milsurp vs. Commercial) — I use both military and commercial brass, having success with each. I do prefer commercial brass as it is easier to prep for the first reload. Military brass usually has a primer crimp of some kind that needs to be removed, and I have found that trimming these cases can sometimes leave you scratching your head as the OAL on military cases varies considerably.
Powder Charge and Dispensing — I have always had good success with Hodgdon H4895 powder. My load has always been right around 47.0 grains, with both the 168gr and 155gr bullets. I also use the Auto-Trickler to drop all of my powder charges. This is a fantastic piece of equipment that not only gives super-consistent powder charges quickly, but it also makes one less thing that you have to worry about while on the firing line. With the Auto-Trickler, there is never a question about the powder charge in your ammo. As for primers, I have been shooting CCI 200 Large Rifle primers for many years and have never had an issue.
Case Care and Trimming — With most of the .30-06 brass that I use, I will only reload them 5 times maximum. I don’t push the brass too much, because the Garand’s semi-auto cycling can be tough on the cases. I also trim my cases for OAL each reload cycle. I use a Giraud power trimmer, so trimming is relatively quick and easy.
The chambers in some of the older rifles are not perfectly-machined like a modern high-end rifle. This can cause the brass to grow a little inconsistently, so I find trimming every load cycle helps to make sure that everything stays in a nice safe spec.
Case Annealing — A few years ago I started to anneal my .223 Rem service rifle brass. Now I have added that process for all my match ammunition. I anneal after every firing. It is a rather easy step as I can have my auto-feeding Annealeez machine running while doing something else, so annealing does not add a great deal of time or effort to the reloading process.
The .30-06 case was the father of the .308 Winchester, which was adopted as the 7.62×51 NATO cartridge.
VIDEO Showcase — Brian Williams Shoots M1903A3 Prone in May 2021
Today we feature a modern switch-barrel PRS chassis rifle set up for quick changes between 6mm Creedmoor and 6.5 Creedmoor barrels. The owner, Forum member Jeff Cosgrove (aka “Punkur67″) uses the 6 CM barrel for competition, favoring the reduced recoil over its 6.5 mm big brother. He does use the 6.5 CM barrel for practice (given its better barrel life). The 6.5 CM barrel also gives him the chance to shoot a variety of factory 6.5 Creedmoor ammo.
- Terminus Zeus action with Quick Change (QC) barrel option.
– 6mm Creedmoor Pre-Fit Bartlein Heavy Varmint 400MODBB barrel for matches
– 6.5 Creedmoor Pre-Fit Benchmark Heavy Palma barrel for training
– MPA BA Competition chassis with full weight kit
– Zero Compromise Optic ZCO 5-27x56mm FFP scope
– TriggerTech Diamond trigger
This rifle represents an evolution for Jeff. Each step along the way in his PRS journey, he has learned more about what he wants and needs in a competition rifle. And what you see here, from the $3760 ZC527 scope to his high-tech reloading equipment, represents pursuit of excellence. Jeff even created a modern, spacious man cave/reloading center in his new house (photos below).
Quick-Change Barrel System with Terminus Zeus QC Action
This rifle has two pre-fit barrels that work with the Terminus Zeus QC Action for fast and easy barrel swaps. To remove a barrel, you simply release two tension screws on the front of the action and then unscrew the barrel. To swap in a different pre-fit barrel, reverse the process and then tension the screws. The Terminus Zeus is 3-lug receiver with 60° bolt and integral recoil lug. Both the receiver and bolt are DLC-treated. Jeff reports this action is extremely smooth and has met all of his expectations. Some other Zeus features are threaded trigger pins for quick/easy trigger installation, and a roller-tipped cocking piece.
PRS Discipline Offers Fun, New Challenge for Long-Time Shooter
My name is Jeff Cosgrove, I live in Winchester, California and do commercial heating and air conditioning. I have shot for 20+ years but I found my interest in shooting was dwindling over time. I got somewhat bored with shooting paper at 100 yards or plinking cans out in the desert. About 18 months ago I decided I wanted to shoot long range. I picked up a used MPA in .300 Winchester Magnum and started shooting long range with a new buddy. That day I fell in love with guns all over again with more intensity than ever.
How I Got Started in PRS
With that new .300 WM I soon found my reloads were not up to my expectations (high ES/SD), so I purchased all new reloading hardware. One of my purchases was a used Benchsource Annealer. The guy I bought that from asked if I had ever tried PRS and he invited me to check out a match. So I went to a local PRS event as a spectator. I looked at many rigs on the firing line and took notes. By the end of the day I knew this was something I really wanted to do. I then acquired a used chassis rifle that I thought would work well for PRS. I went to a PRS match the following month but shot poorly.
After working with that first PRS rifle, a 6.5 CM with Stiller Tac30 action, MDT chassis, and Proof Carbon-wrapped barrel, I quickly learned that gun did not handle and balance the way I hoped.* It was too light in the front, the ergos were poor, and scope eye relief was not optimal. So I decided to build my own GEN 2 PRS rifle. This is the story of how I put together my new switch-barrel rig that I now use in competition.
PRS Rifle and Gear Selection — Learning What Works
Barrel availability was limited given the current shortages. Luckily I was able to obtain a 6mm Creedmoor pre-fit Bartlein Heavy Varmint 400MODBB from Southern Precision Rifles. The 6mm Creedmoor is notorious for being a barrel burner cartridge so I went with the special 400MODBB metal. Bartlein says that barrel life expectancy is 1.5 to 2 times longer than the standard 416 grade steel. I also purchased a 6.5 Creedmoor pre-fit Benchmark Heavy Palma barrel for training (Source: Straight Jacket Armory). With the Terminus Zeus quick change system I am able to swap from my match barrel to my trainer barrel in just a couple minutes. I loosen two set screws, unthread the barrel, thread the new barrel on, and torque the set screws to 10 inch-pounds. This also affords me caliber options in case I’m in a pinch for ammo. If I have some 6.5 CM loaded up and don’t have time to load 6mm Creedmoor for a match, then I’m covered.
For the trigger, I went with a TriggerTech Diamond Pro curve model. I have Timney, Jewell, and TriggerTech triggers in other rifles. I like them all but I liked the feel of the TT Diamond the best so that is what I used on this build. I set my triggers around 18-20 oz. — I am not a fan of ultra-light trigger pulls.
MPA BA Competition Chassis with Added Weight
I went with an MPA BA Comp chassis with full internal and external weight kit. I also have Gray Ops external weight on the handguard. I had the same chassis on my .300 WinMag and felt very comfortable with it. I took a PR1 class and found that, with a different gun, I had to force a comfortable hand position for proper trigger pull. After that class I grabbed my MPA and my hand fell in to the perfect position. I did not need to hunt or index my hand with the MPA. The built ARCA rail (RAT) lowered the rifles center of gravity more than my old setup with the ARCA rail bolted to the bottom of the handguard. With the current configuration, the rifle weighs in at 24 lbs. and balances three inches in front of the magwell. I now have the flexibility to add, subtract, or move approximately 6 lbs. of weight.
The Attraction of PRS/NRL Practical Competitions
I really enjoy PRS-style shooting because there seems to be a new challenge every time you compete — no matter what. With PRS I am shooting many different positions and ranges with the pressure of a stopwatch. This keeps things interesting for me. I have taken a few training classes to help establish good, clean fundamentals.
Jeff says it is hard to practice for the many unconventional shooting positions at PRS matches.
My biggest challenges so far have been: 1) building stable shooting positions that I have not practiced enough; 2) proper equipment selection; and 3) time management. Regarding the shooting positions — PRS/NRL is not like F-Class where you can always practice from one position. And it’s hard to practice for unusual set-ups (barriers and positions) you’ve not encountered before. Concerning equipment — you need some experience in the game to determine what really works best for you.
Innovative Zero Compromise Optic — Optimized for the Tactical Game
The scope is a Zero Compromise ZC527 (5-27x56mm FFP) with MPCT2 reticle. Zero Compromise Optic is a relatively new manufacturer, but their scopes are top-flight. The First Focal Plane ZCO has excellent glass that is extremely bright and clear. With a big 36mm main tube, the ZC527 offers 35 Mils Elevation and 21 Mils Windage adjustment. The field of view is 21 feet at 100 yards — one of the widest in the industry. The ZC527 also offers illuminated reticle and locking turrets. When I was at my first PRS match I looked through several different scopes. When I got behind a ZCO scope I knew this was what I wanted — the ZCO scope was super clear, super sharp, with very positive controls.
I put a protective wrap on the scope because with some of our PRS stages it is easy to scratch or dent the scope tube. You don’t want to bang up an expensive scope — the ZC527 retails for $3760.
Reloading for 6mm Creedmoor and 6.5 Creedmoor
When starting out with a new cartridge I like to search places like AccurateShooter.com and UltimateReloder.com for popular recipes used by knowledgeable shooters. I am all about paving your own way on certain things but with the consistency, higher cost, and limited supply of components these days I try to stick with the most common loads. I also want to limit barrel wear and get through load development quickly. I don’t want to chase loads for 300 rounds to ultimately land in the same place that so many other people have already found.
I start my new barrels with virgin brass and load three rounds at each charge weight in 0.2 grain increments. I put the most popular charge weight (for my chosen bullet) in the middle of my load range and load above and below to find a good node while paying close attention for pressure signs along the way. I use the 6.5 Guys spreadsheet (see below) to help analyze my results. With those results I like to re-test a narrower range with 5-10 rounds each charge weight in 0.2 grain increments. I again use the 6.5 Guys spreadsheet to make a final charge weight selection and then I move on to seating depth. I will load different depths to tighten the groups up.
Load Development Using 6.5 Guys Custom Spreadsheet
To hold and analyze my load development data I use the spreadsheet from 65Guys.com. It helps a ton with making a decision on your final load. This Excel spreadsheet works great and makes it simple to analyze your data. You can even copy and paste your chronograph data if your chrono logs on to a SD card.
In this 6.5 Guys video Steve provides an overview and tutorial for using the Excel load development analysis model that he has developed. The Excel Load Development Analysis Spreadsheet version 2.0 is FREE. Download from the 6.5 Guys Website.
In this video Steve explains some key statistical concepts for performing load data analysis. He also provides tips and guidance for determining the optimal load for your rifle as you analyze the load data you’ve collected.
New House, New Man Cave/Reloading Room
Jeff recently moved with his family into a great new house. One bonus of this move was that he upgraded from a cramped reloading area to a dedicated “Man Cave” that has ample space for his gun safes, multiple presses, and all his reloading components. Large upper and lower cabinets plus a dedicated “gun closet” provide plenty of storage. Read all about this move in this AccurateShooter Forum Thread.
Here is Jeff’s first reloading area years ago: “My first reloading setup was smashed in my two-bedroom condo so I had a very small bench that was very cluttered. I had to deal with the limited space I had but I made it work. Then in our first house I had a larger bench/cabinet, but it was still not ideal.”
Here is the new Man Cave in the new house — very open, spacious, with plenty of storage.
This animated GIF shows the new Man Cave move-in process start to finish:
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.
The shape of powder grains has a profound effect on the performance of the powder charge, as it concerns both pressure and velocity. There are multiple powder shapes including flake, ball, and extruded or “stick” (both solid and perforated).
So how does powder grain shape affect pressure and muzzle velocity?
In general, it can be said that powder that burns progressively achieves a desired muzzle velocity at lower maximum pressure than a powder that burns neutrally, not to mention a degressive powder. As grain size increases, the maximum pressure moves towards the muzzle, also increasing muzzle blast. Muzzle velocity and pressure can be adjusted by means of the amount of powder or loading density, i.e. the relationship between the powder mass and the volume available to it. As the loading density increases, maximum pressure grows.
All Vihtavuori reloading powders are of the cylindrical, single-perforated extruded stick type. The differences in burning rate between the powders depend on the size of the grain, the wall thickness of the cylinder, the surface coating and the composition. Cylindrical extruded powders can also have multi-perforated grains. The most common types are the 7- and 19-perforated varieties. A multi-perforated powder grain is naturally of a much larger size than one with a single perforation, and is typically used for large caliber ammunition.
Other types of powder grain shapes include sphere or ball, and flake. The ball grains are typically used in automatic firearms but also in rifles and handguns. The ball grain is less costly to produce, as it is not pressed into shape like cylindrical grains. Flake shaped grains are typically used in shotgun loadings.
Web thickness in gunpowder terminology means the minimum distance that the combustion zones can travel within the powder grain without encountering each other. In spherical powders, this distance is the diameter of the “ball”; in flake powder it is the thickness of the flake; and in multi-perforated extruded powders it is the minimum distance (i.e. wall thickness) between the perforations.
The burning rate of powder composed of grains without any perforations or surface treatment is related to the surface area of the grain available for burning at any given pressure level. The change in the surface area that is burning during combustion is described by a so-called form function. If the surface area increases, the form function does likewise and its behavior is termed progressive. If the form function decreases, its behavior is said to be degressive. If the flame area remains constant throughout the combustion process, we describe it as “neutral” behavior.
The cylindrical, perforated powders are progressive; the burning rate increases as the surface area increases, and the pressure builds up slower, increasing until it reaches its peak and then collapses. Flake and ball grains are degressive; the total powder surface area and pressure are at their peak at ignition, decreasing as the combustion progresses.
Here’a useful article by Sierra Bullets Media Relations Manager Carroll Pilant. This story, which originally appeared in the Sierra Bullets Blog, covers some of the more common ammo problems that afflict hand-loaders. Some of those issues are: excessive OAL, high primers, and improperly-sized cases. Here Mr. Pilant explains how to avoid these common problems that lead to “headaches at the range.
I had some gentlemen at my house last fall getting rifle zeros for an upcoming elk hunt. One was using one of the .300 short mags and every 3rd or 4th round would not chamber. Examination of the case showed a bulge right at the body/shoulder junction. These were new cases he had loaded for this trip. The seating die had been screwed down until it just touched the shoulder and then backed up just slightly. Some of the cases were apparently slightly longer from the base to the datum line and the shoulder was hitting inside the seating die and putting the bulge on the shoulder. I got to thinking about all the gun malfunctions that I see each week at matches and the biggest percentage stem from improper handloading techniques.
One: Check Your Cases with a Chamber Gage
Since I shoot a lot of 3-gun matches, I see a lot of AR problems which result in the shooter banging the butt stock on the ground or nearest solid object while pulling on the charging handle at the same time. I like my rifles too well to treat them that way (I cringe every time I see someone doing that). When I ask them if they ran the ammo through a chamber gage, I usually get the answer, “No, but I need to get one” or “I didn’t have time to do it” or other excuses. The few minutes it takes to check your ammo can mean the difference between a nightmare and a smooth running firearm.
A Chamber Gauge Quickly Reveals Long or Short Cases
Size Your Cases Properly
Another problem is caused sizing the case itself. If you will lube the inside of the neck, the expander ball will come out a lot easier. If you hear a squeak as the expander ball comes out of a case neck, that expander ball is trying to pull the case neck/shoulder up (sometimes several thousandths). That is enough that if you don’t put a bulge on the shoulder when seating the bullet … it can still jam into the chamber like a big cork. If the rifle is set up correctly, the gun will not go into battery and won’t fire but the round is jammed into the chamber where it won’t extract and they are back to banging it on the ground again (with a loaded round stuck in the chamber). A chamber gage would have caught this also.
Oversizing cases also causes problems because the firing pin doesn’t have the length to reach the primer solid enough to ignite it 100% of the time. When you have one that is oversized, you usually have a bunch, since you usually do several cases at a time on that die setting. If the die isn’t readjusted, the problem will continue on the next batch of cases also. They will either not fire at all or you will have a lot of misfires. In a bolt action, a lot of time the extractor will hold the case against the face of the breech enough that it will fire. The case gets driven forward and the thinner part of the brass expands, holding to the chamber wall and the thicker part of the case doesn’t expand as much and stretches back to the bolt face. If it doesn’t separate that time, it will the next time. When it does separate, it leaves the front portion of the case in the chamber and pulls the case head off. Then when it tries to chamber the next round, you have a nasty jam. Quite often range brass is the culprit of this because you never know how many times it has been fired/sized and in what firearm. Back to beating it on the ground again till you figure out that you have to get the forward part of the case out.
Just a quick tip — To extract the partial case, an oversized brush on a cleaning rod [inserted] and then pulled backward will often remove the case. The bristles when pushed forward and then pulled back act like barbs inside the case. If you have a bunch of oversized case that have been fired, I would dispose of them to keep from having future problems. There are a few tricks you can use to salvage them if they haven’t been fired though. Once again, a case gage would have helped.
Two: Double Check Your Primers
Another thing I see fairly often is a high primer, backwards primer, or no primer at all. The high primers are bad because you can have either a slam fire or a misfire from the firing pin seating the primer but using up its energy doing so. So, as a precaution to make sure my rifle ammo will work 100% of the time, I check it in a case gage, then put it in an ammo box with the primer up and when the box is full, I run my finger across all the primers to make sure they are all seated to the correct depth and you can visually check to make sure none are in backwards or missing.
Three: Check Your Overall Cartridge Length
Trying to load the ammo as long as possible can cause problems also. Be sure to leave yourself enough clearance between the tip of the bullet and the front of the magazine where the rounds will feed up 100%. Several times over the years, I have heard of hunters getting their rifle ready for a hunt. When they would go to the range to sight in, they loaded each round single shot without putting any ammo in the magazine. On getting to elk or deer camp, they find out the ammo is to long to fit in the magazine. At least they have a single shot, it could be worse. I have had hunters that their buddies loaded the ammo for them and then met them in hunting camp only to find out the ammo wouldn’t chamber from either the bullet seated to long or the case sized improperly, then they just have a club.
Four: Confirm All Cases Contain Powder
No powder in the case doesn’t seem to happen as much in rifle cartridges as in handgun cartridges. This is probably due to more handgun ammo being loaded on progressive presses and usually in larger quantities. There are probably more rifle cartridges that don’t have powder in them than you realize though. Since the pistol case is so much smaller internal capacity, when you try to fire it without powder, it usually dislodges the bullet just enough to stick in the barrel. On a rifle, you have more internal capacity and usually a better grip on the bullet, since it is smaller diameter and longer bearing surface. Like on a .223, often a case without powder won’t dislodge the bullet out of the case and just gets ejected from the rifle, thinking it was a bad primer or some little quirk.
For rifle cases loaded on a single-stage press, I put them in a reloading block and always dump my powder in a certain order. Then I do a visual inspection and any case that the powder doesn’t look the same level as the rest, I pull it and the one I charged before and the one I charged after it. I inspect the one case to see if there is anything visual inside. Then I recharge all 3 cases. That way if a case had powder hang up and dump in the next case, you have corrected the problem.
On progressive presses, I try to use a powder that fills the case up to about the base of the bullet. That way you can usually see the powder as the shell rotates and if you might have dumped a partial or double charge, you will notice as you start to seat the bullet if not before. On a progressive, if I don’t load a cartridge in one smooth stroke (say a bullet tipped over sideways and I raised the ram slightly to reset it) Some presses actually back the charge back adding more powder if it has already dumped some so you have a full charge plus a partial charge. When I don’t complete the procedure with one stroke, I pull the case that just had powder dumped into it and check the powder charge or just dump the powder back into the measure and run the case through later.
Most of us own a .223 Rem rifle. Now, thanks to our friends at Rifleshooter.com we can assess exactly how velocity changes with barrel length for this popular cartridge.
Rifleshooter.com performed an interesting test, cutting the barrel of a .223 Rem rifle from 26″ all the way down to 16.5″. The cuts were made in one-inch intervals with a rotary saw. At each cut length, velocity was measured with a Magnetospeed chronograph. To make the test even more interesting, four different types of .223 Rem/5.56 ammo were chron’d at each barrel length. The Rifleshooter.com team that conducts these tests has a full-service gun shop, 782 Custom Gunworks — visit 782guns.com.
Test Barrel Lost 25.34 FPS Per Inch (.223 Rem Chambering)
How much velocity do you think was lost, on average, for each 1″ reduction in barrel length? The answer may surprise you. The average speed loss of the four types of .223/5.56 ammo, with a 9.5″ shortening of barrel length, was 240.75 fps total (from start to finish). That works out to an average loss of 25.34 fps per inch.
5.56/.223 Barrel Cut-Down Speed Test 26″ to 16.5″
Start FPS at 26″
End FPS at 16.5″
Total Loss
Average Loss Per Inch
UMC .223 55gr
3182*
2968
214
22.5 FPS
Federal M193 55gr
3431
3187
244
25.7 FPS
Win m855 62gr
3280
2992
288
30.3 FPS
Blk Hills .223 68gr
2849
2632
217
22.8 FPS
*There may have been an error. The 25″ velocity was higher at 3221 fps.
Rifleshooter.com observed: “Cutting the barrel from 26″ to 16.5″ resulted in a velocity reduction of 214 ft/sec with the UMC 223 55-grain cartridge, 244 ft/sec with the Federal M-193 cartridge, 288 ft/sec with the Winchester M855 cartridge and 217 ft/sec with the Back Hills 223 68-grain match cartridge.”
How the Test Was Done
The testers described their procedure as follows: “Ballistic data was gathered using a Magnetospeed barrel-mounted ballistic chronograph. At each barrel length, the rifle was fired from a front rest with rear bags, with five rounds of each type of ammunition. Average velocity and standard deviation were logged for each round. Once data was gathered for each cartridge at a given barrel length, the rifle was cleared and the bolt was removed. The barrel was cut off using a cold saw. The test protocol was repeated for the next length. Temperature was 45.7° F.”
See More Barrel Cut-Down Tests on Rifleshooter.com
Rifleshooter.com has performed barrel cut-down tests for many other calibers/chamberings including 6mm Creedmoor, .308 Winchester, and .338 Lapua Magnum. See these test results at Rifleshooter.com.
Much Different Results with 6mmBR and a Longer Barrel
The results from Rifleshooter.com’s .223/5.56 test are quite different than the results we recorded some years ago with a barrel chambered for the 6mmBR cartridge. When we cut our 6mmBR barrel down from 33″ to 28″ we only lost about 8 FPS per inch. Obviously this is a different cartridge type, but also our 6mmBR barrel end length was longer than Rifleshooter.com’s .223 Rem start length. Velocity loss may be more extreme with shorter barrel lengths. And, of course, different cartridge types and powder/bullet combinations will yield different results.
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.
Norma has released a fascinating video showing how bullet, brass, and ammunition are produced at the 
Bullet Selection — With the .30-06 for my Garands and Springfields I stick mostly with 168gr bullets plus some 155-grainers. These bullet weights have just worked for me in the past. 
Powder Charge and Dispensing — I have always had good success with Hodgdon H4895 powder. My load has always been right around 47.0 grains, with both the 168gr and 155gr bullets. I also use the Auto-Trickler to drop all of my powder charges. This is a fantastic piece of equipment that not only gives super-consistent powder charges quickly, but it also makes one less thing that you have to worry about while on the firing line. With the Auto-Trickler, there is never a question about the powder charge in your ammo. As for primers, I have been shooting CCI 200 Large Rifle primers for many years and have never had an issue. 
Oversizing cases also causes problems because the firing pin doesn’t have the length to reach the primer solid enough to ignite it 100% of the time. When you have one that is oversized, you usually have a bunch, since you usually do several cases at a time on that die setting. If the die isn’t readjusted, the problem will continue on the next batch of cases also. They will either not fire at all or you will have a lot of misfires. In a bolt action, a lot of time the extractor will hold the case against the face of the breech enough that it will fire. The case gets driven forward and the thinner part of the brass expands, holding to the chamber wall and the thicker part of the case doesn’t expand as much and stretches back to the bolt face. If it doesn’t separate that time, it will the next time. When it does separate, it leaves the front portion of the case in the chamber and pulls the case head off. Then when it tries to chamber the next round, you have a nasty jam. Quite often range brass is the culprit of this because you never know how many times it has been fired/sized and in what firearm. Back to beating it on the ground again till you figure out that you have to get the forward part of the case out.
