Cartridges: Long Range Reloading Safety - .308 and Others

Long-Range Reloading Safety - .308 and Others
by Germán A. Salazar

This article is Part 5 of our series on reloading the .308 cartridge for the Palma course and other long-range matches. In Part 1, we discussed various bullet choices and the sometimes tedious process of real-life load testing with its inherent limitations. In Part 2 we introduced the basic problem with the .308 at 1000 yards - keeping it above 1.2 mach - and covered my thoughts on component selection and brass preparation for the .308. Part 3 of the series cautioned against simply copying another shooter's load, presented the techniques for determining the minimum MV necessary to remain above 1.2 mach, and showed range reloading as a useful method of reaching that MV safely. In Part 4 we focused on pressure factors by showing the dramatic range of case capacity in .308 brass of different makes and also demonstrating the capacity differences caused by changes in throat length and resultant seating depth variances. If you haven't read the first four articles in the series, I urge you to do so as they provide the background for this final installment. 

As we have seen, the .308's limited case capacity for its bore size presents some special problems for the handloader seeking safe, accurate, reliable ammunition for use at 1000 yards. Frankly, it's a poor choice for that application, but in many instances we are required to use it, so we must find a way to make it work - and work safely. Handloads with excessive pressure are an all too common danger on the range; not only do they present a danger to the shooter, but also to the shooter lying next to him and to the host club. We should all be a vigilant for and intolerant of shooters with loads that are constantly blowing primers, having to pound their bolts open, blowing up bullets and other indications of unsafe loads.  Their irresponsible practices could seriously injure you and cost your club its financial future. The information presented in this series, as well as some common sense, should keep you from those troubles when loading a marginal cartridge such as the long-range .308. Unsafe loading practices aren't limited to the .308, of course, and it is frustrating to see so much of it on the range these days - it is a senseless danger to our sport.

Incomplete Information
Take a good look at these two Remington bolts. The one on the right, from one of my rifles, has seen about 50,000 rounds, over a dozen barrels in various cartridges (most in .308) and has never been touched other than regular cleaning. The one on the left, from a friend's rifle, was fired about 3,000 rounds of .308, many of these loads excessive pressure; the final one wildly excessive, causing much of the damage shown. Note the burn marks from blown primers, the missing ejector plunger, the mangled case head recess, the torn extractor - think this couldn't happen to you?

How did this event occur?  Simple - the shooter heard another shooter say that his Palma load was XX grains of YY powder with a ZZ gr. bullet.  He didn't get much more in the way of details and decided to copy the load. Unfortunately, he used brass with a lower case capacity (Lapua instead of Winchester), bullets with a longer bearing surface (Sierra instead of Berger) and a chamber with a shorter throat.  All of these pressure factors worked against him (just as we reviewed in Part 4).  There were warnings, as the load blew primers right from the start, but he didn't heed them.

The shooter of the rifle in question is a very lucky fellow. He is lucky to have escaped injury when the rifle finally said "enough." A good deal of that luck comes from the fact that he was shooting a tubegun with the action glued-in to the center sleeve. The sleeved action was less likely to rupture, and the tubegun design kept his face was well above all the high-pressure gas that vented out not only on the final shot, but on many of the preceding ones that should have warned him to quit. I said lucky, not smart... And yet, this shooter really is a smart person in his personal and professional life - he simply failed to apply a bit more of that intelligence as well as some common sense to his reloading.
Pressure Signs
I've been very fortunate to have access to an Oehler 43 system to measure pressure in handloads and I have truly learned vast amounts from its use. The main thing I've learned is that up to about the SAAMI maximum pressure of 60,000 psi for most modern cartridges, including the .308, you usually won't see any pressure signs such as ejector marks on brass, hard bolt lift (assuming proper case resizing) or flattened primers. Once you begin to see those signs, it's really time to back the load down.

Look at these three case heads (click to enlarge). The one on the left shows a slight ejector mark and that's a good warning to back the load down a bit. The middle one has a heavier ejector mark and also an extractor mark from the Sako type extractor, this one really needs to go down. The third one is the remnant of the last case fired with the damaged bolt shown above; based on my pressure testing experience, I have to say that there is no way that load was under 100,000 psi - yes, he was lucky indeed. You might not be so lucky.

Careless Assumption
How do you like this one? This is what's left of the breech end of the barrel of that used to be on a fine custom action. Actually, the action's tremendous strength and good gas handling design saved this shooter from serious injury, but he was very shaken up. Although the manufacturer was able to remove the barrel (with extensive damage to the action threads), the bolt never opened again and the action had to be scrapped. Care to guess at the pressure? This happened to a very experienced reloader who had a moment of carelessness and used a mislabeled powder. It didn't look right, he told me, but the label was right so he assumed...

It's the Brass
What's especially instructive here is the very visible mode of failure - the cartridge case blew out at the extractor. Every action leaves some portion of the case unsupported, otherwise it would be impossible for an extractor to snap over the rim. The Remington 700 design is about as good as it gets as long as the original extractor is used; all others leave even more unsupported area. And this, you see, is ultimately the real problem with excessive pressure loads - it doesn't matter how thick your action is or how big the bolt is, it is that thin sliver of unsupported brass that will yield and put 60,000 psi, or more, of hot gas into your face. It's the brass, and you can't do anything about it! That's why the SAAMI limit is not dependent on the specific action - it's the brass.

I mentioned above that even a slight ejector mark is a warning that you are into an excessive pressure situation.  I hope that you now begin to understand why that is so. An ejector mark, or a sticky bolt lift, is a sign that the brass is deforming past its elastic limit; it is now approaching failure.

Beat On It Till It Breaks
Another shooter in our area recently had the whole firing pin assembly on his rifle exit the bolt rearward and smash into his face. That required hospitalization and I would not class the injury as minor. He was shooting a .223 bolt action rifle and frequently blowing primers. Each time a primer blows, the firing pin acts like a projectile driven rearward by the gas until it slams into the shroud or cocking piece with huge force. Eventually, the retaining mechanism yielded and the whole firing pin assembly became the projectile and our friend's face the target.

Do It Right
At left is a set of fired cases from my Palma rifle. They've been fired 10 times with a Berger 175 at an MV that retains 1.263 mach at the target from 1000 yards. Notice that there are no ejector marks, no extractor marks, the primers have a nice edge radius and there is no cratering on the primers. There's no magic to this, just careful reloading practices following the concepts presented in this series. I really enjoy match shooting, but I enjoy going home after the match instead of to the hospital even more.

If you read through the articles in this series and many of the others on this site, you'll also discover a very fundamental truth about ballistics: once you have selected the cartridge case and the bullet, there is really no practical gain in wind drift from a load with excessive pressure.  You are simply increasing both the danger level and the expected group size. That last point is worth dwelling on for a moment - once a load passes a certain point, reliable accuracy diminishes and that point is usually well below maximum pressure. I'm often asked how I get such high X counts from the .30-06 (usually 36X to 44X for a 60 shot iron sight mid-range match). The answer is that it takes a moderate load, a reliably accurate bullet and perfect wind reading and shot execution. Every time I try increasing the load a bit, I see the X count drop. The .308 is exactly the same, although we have to get a bit closer to maximum pressure when loading it for long-range shooting to make the magic number.

A Bit of Philosophy
Are you a Rifleman? I've been involved in competitive shooting for 40 years and all that time, as an NRA member, I've received the American Rifleman every month. The word "Rifleman" captured my imagination as a boy and it captures the essence of why I shoot: I want to be a master of the art, the craft, the science of rifle shooting. At long-range, being a Rifleman requires being a master wind-reader; that's precisely why I avoid the big barrel-burning cartridges. I measure my success or failure by how well I measure up to the challenge presented by the wind, not by how little wind drift I was able to build into a cartridge. That's also the reason I don't shoot with a scope in any-sight matches; as I see it, the scope eliminates one of the more significant challenges that Riflemen have historically faced. How interesting is a boxing match between a heavyweight and a welterweight? Not very interesting. I want a fair fight with the wind, I want to push myself physically and mentally, I want to see what I can accomplish as a Rifleman. The rifle and the load are simply the tools with which I test myself and I don't want them to mask my failure or to take the credit for my success.


All contents Copyright 2012 The Rifleman's Journal