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.
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What you see above is what happens when you shoot the wrong powder in a muzzle-loader. Specifically, a charge of smokeless powder was used instead of black powder or black powder substitute. The difference in energy (by weight and volume) between black powder and modern smokeless powder is huge. You should never, ever run smokeless powder in a black powder recipe. The result can be catastrophic. In this case the hapless shooter lost a couple fingers. So he got a free twin-digit amputation, thanks to his reloading mistake. The lesson to learn here is to always double-check your propellant before loading. And never “re-bottle” smokeless powder into a different container with a different label (or worse yet, no label at all).
This incident happened in Indiana a couple years back. As reported by the Indiana Dept. of Natural Resources (DNR), this was a classic case of “user error”: “Corporal Eric Doane worked a firearm accident last night in Martin County that resulted in the shooter losing a couple fingers. This is what can happen when you shoot smokeless powder out of a muzzle-loader designed for black powder.”
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.
The researchers ensure their data is safe with the bullet yielding the highest pressure. Thus, all others in that group should produce equal or less pressure, and they are safe using this data.
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.
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Here are some really smart tips for hand-loaders compiled by Sierra Bullets. These suggestions were submitted by Sierra’s Facebook fans — and some are very valuable indeed. Some of these tips will help you load more accurate ammo. Other selections will help you stay SAFE — which should always be your #1 priority. For example, we concur with the advice to “Check and Double Check. Everything. Every Time”. Also definitely keep “One powder on the bench at a time” — that could be a life-saver. You may want to print these “words of wisdom” and place them on a wall in your loading room.
Reloading Safety Tips — Sound Advice
ALWAYS START LOW: “Just because a load manual says X grains of X powder with X bullet is max, your rifle could reach max pressure a grain or two before what the book says. Start low and work up.” — Walter Coats
BE SAFE and CAREFUL: “Check and double check. Everything. Every time. Only one type of powder on the bench at a time.” — Glen Lundgren
DON’T RUSH: “Be patient, don’t be in a hurry, have fun and find your rhythm. Just tell your family you’re putting yourself in ‘time-out’. They will understand.” — Erik Dyal
POWDER RULE #1: “One powder on the bench at one time, it might save your life.” — James A. Kimery
STAY FOCUSED: “Relaxed but concentrated attention. Have fun enjoying a great hobby and pastime but stay focused.” — Jim Caldwell
POLICE LOADING AREA: “Keep your reloading bench area clean and put items away ASAP.” — Eric J. Ford
BE PATIENT: “Focus, Focus, Focus — be patient — it AIN’T a race.” — William Stanley
RECORD YOUR LOADS: “Write down on a small card what you’re loading – bullet weight, powder weight, type of powder, and primer. And put it in the powder hopper. I am unloading .45 FMJ because I forgot what type powder was in the hopper.” — Michael Conniff
HAVE a PROCEDURE for INTERRUPTIONS: “If, for any reason, you have to leave the bench while in the process of dropping powder charges, turn the next case to be charged upside down in the loading block so you know where you left off.” — Bill Tinsley
LABEL EVERYTHING: “OCD is a good habit to have with your loading bench. CLEARLY label everything!” — Andy Pynckel
HAVE a GOAL: “Never start reloading or developing a load without a specific goal in mind. Second keep meticulous records.” — Peter Eick
RESEARCH THE JOB: “Read all you can about it before you start!” — Keith Shively
KEEP TRACK of the Brass: “I put all my primed brass upside down (primer up) and as I charge the casing, I (of course) flip it primer down.” — Mark Ewing
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What you see above is what happens when you shoot the wrong powder in a muzzle-loader. Specifically, a charge of smokeless powder was used instead of black powder or black powder substitute. The difference in energy (by weight and volume) between black powder and modern smokeless powder is huge. You should never, ever run smokeless powder in a black powder recipe. The result can be catastrophic. In this case the hapless shooter lost a couple fingers. So he got a free twin-digit amputation, thanks to his reloading mistake. The lesson to learn here is to always double-check your propellant before loading. And never “re-bottle” smokeless powder into a different container with a different label (or worse yet, no label at all).
This incident happened in Indiana a couple years back. As reported by the Indiana Dept. of Natural Resources (DNR), this was a classic case of “user error”: “Corporal Eric Doane worked a firearm accident last night in Martin County that resulted in the shooter losing a couple fingers. This is what can happen when you shoot smokeless powder out of a muzzle-loader designed for black powder.”
RCBS makes some of the most rugged and durable reloading products you can buy. The RCBS Rock Chucker press is legendary — for good reason. The Editor uses one that has been in my family over twenty years. I also own an RCBS 2000 progressive press that has loaded many thousands of rounds, and features the excellent APS strip priming system. RCBS is serious about reloading, so this company has created a very complete series of instructional videos showing reloading precedures and equipment. You’ll find over 60 videos on the RCBS Video Resources Page and RCBS YouTube Channel.
We encourage readers to check out the RCBS Videos. They can help you master the basics of handloading — case prep, priming, sizing, and bullet seating. In addition, these videos can help you select the right equipment for your loading bench. Videos show presses, case tumblers, ultrasonic cleaning machines, powered case prep centers, and more.
Here are three of our favorite RCBS Reloading videos, along with links to a dozen more:
Basic Safety Precautions for Reloading
Every novice hand-loader should watch this video. It covers the key safety principles you should follow, such as “Don’t use components of unknown origin”. We would add — always double check the labels on your powder bottles, and if you don’t know 100% what powder is in your powder measure — dump it out. Some of the most serious injuries have occurred when reloaders put pistol powder in rifle cases.
Setting Up the Sizing Die Correctly
This video address the common complaint some novices have when their hand-loadeed cartridges won’t chamber properly. Kent Sakamoto explains how to set up the sizing die properly to size the case body and bump the shoulder.
Choosing a Case Cleaning System
Here Kent Sakamoto looks at the three main types of brass cleaning systems: Vibratory Tumbler, Wet Tumbler (with media), and Ultrasonic Cleaning Machine. Kent reviews the pros and cons of each system.
More RCBS Reloading Videos
Here are twelve more helpful videos from RCBS. These cover both reloading techniques and reloading equipment. There are currently over 60 videos on the RCBS YouTube Channel.
The anvil is the tripod-shaped thin metal piece protruding above the bottom of the primer cup. Getting the primer sitting fully flush on the bottom of the case primer pocket, without crunching it too much, requires some keen feel for the progress of primer seating.
In two recent Midsouth Blog articles, Glen Zediker offers helpful advice on priming. First he examines what happens to the primer itself as it is seated in the cup. Glen explains why some “crush” is important, and why you never want to leave a high primer. Glen also reviews a variety of priming tools, including his favorite — the Forster Co-Ax Bench Primer Seater. Then he offers some key safety tips. Glen provides some “rock-solid” advice about the priming operation. You’ll find more great reloading tips in Glen’s newest book, Top-Grade Ammo, which we recommend.
Priming Precision vs. Speed
Glen writes: “The better priming tools have less leverage. That is so we can feel the progress of that relatively very small span of depth between start and finish. There is also a balance between precision and speed in tool choices, as there so often is.”
Benchtop Priming Tools — The Forster Co-Ax
Glen thinks that the best choice among priming options, considering both “feel” and productivity, may be the benchtop stand-alone priming stations: “They are faster than hand tools, and can be had with more or less leverage engineered into them. I like the one shown below the best because its feeding is reliable and its feel is more than good enough to do a ‘perfect’ primer seat. It’s the best balance I’ve found between speed and precision.”
Load Tuning and Primers
Glen cautions that you should always reduce your load when you switch to a new, not-yet-tested primer type: “The primer is, in my experience, the greatest variable that can change the performance of a load combination, which is mostly to say ‘pressure’. Never (never ever) switch primer brands without backing off the propellant charge and proving to yourself how far to take it back up, or to even back it off more. I back off one full grain of propellant [when I] try a different primer brand.”
Priming Safety Tips by Zediker
1. Get a good primer “flip” tray for use in filling the feeding magazine tubes associated with some systems. Make double-damn sure each primer is fed right side up (or down, depending on your perspective). A common cause of unintentional detonation is attempting to overfill a stuffed feeding tube magazine, so count and watch your progress.
2. Don’t attempt to seat a high primer more deeply on a finished round. The pressure needed to overcome the inertia to re-initiate movement may be enough to detonate it.
3. Don’t punch out a live primer! That can result in an impressive fright. To kill a primer, squirt or spray a little light oil into its open end. That renders the compound inert.
4. Keep the priming tool cup clean. That’s the little piece that the primer sits down into. Any little shard of brass can become a firing pin! It’s happened!
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!
