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GUNS Magazine March 2012 Digital Edition - Page 20
STORY: Glen Zediker Load deveLoPMent Crucial to accurate, consistent handloads. usually talk here about guns. But, dang, guns are little to no fun at all without ammunition. I thought for this bit it might help some to talk about the process of developing a handload for your AR-15. New bullet, new propellant, new rifle—anything new means testing and development. For myriad reasons, some known and some I’m not so sure about, one load may perform differently in different rifles, and this new jug of propellant or box of primers may not behave the same as the last batch of the “same” thing. I do all my load work at the range. That’s another article by itself, but it lets me not only save a whopping lot of time, but also have the opportunity to test combinations under pretty consistent conditions. There are a number of good loading manuals. Most are done either by bullet or propellant manufacturers, and there’s a lot more data available via magazines. Study enough of it and it becomes plain agreement is unusual. The reason is because of differences in components and equipment, and also testing conditions or circumstances. Published data serves me mostly by establishing an idea of what to anticipate—an important function. A number of variables apply to a cartridge (propellant, bullet, primer, case), and then an increasingly escalating number of variables introduced through variously combining and fine-tuning all those (bullet seating depth, for example). Reduce variables to a minimum to get accurate feedback from testing. Let’s focus on propellant charge. primers seat into the resized cases. A hand-style priming tool is really necessary to get accurate feedback. If the primer enters the pocket more easily than normal, that’s a very good indication that load is running hot. There’s only one caveat. Brass has a “memory.” A case may not fully expand with lighter “starting” loads. Cases fire-formed with lighter charges should not be reused with heavier charges. Many disagree, but my experience has been that can result in shorter case life and possibly even case failure. “Lighter” and “heavier” depends on the range of propellant weights tried in the test. For a yardstick, cases first-fired within one full grain of propellant of the maximum load, or we could call it 100 fps, are OK to reuse for uppervelocity reloads. Judging fired primer condition is a common means to gauge pressure. I habitually look at the spent primer on each case coming out of the rifle chamber during testing. Not all combinations clearly reveal the visible clues we watch for: excessive flattening, cratered surface, or cracks and pierces. That depends, it seems, a lot on the primer brand, and generally, small rifle primers may not show as “much” as large rifle primers, or won’t until pressure levels are comparatively higher. I will say if you see anything that looks like an over-pressure symptom show in a primer, you better believe it’s telling the truth. In a load that’s not overpressure, there should be a radius on the edge of a fired primer. The best immediate indication though, is bullet velocity. A chronograph really needs to be part I Glen does all his load work at the range. A good powder meter is a must to get reliable results from an incremental test. This (above) is from Harrell’s Precision. If you encounter any pressure symptoms—any—back the load off a 1/2 grain. If you see any more, back it off another 1/2 grain. Don’t come back a 1/10 or two and think you’re OK, even if the signs don’t return. If visible pressure signs appear, the load isn’t just a little over pressure, it’s a lot over pressure. This is especially true given the experience of a load that seemed fine and then, on another day, showed pressure signs. Guess what? It was already over pressure, and the question is always how much. Keep it safe It’s best to do load testing with new brass because it gives a better indication of pressure than a previously fired case will. The primer pocket tells you the most. It’s easy to gauge what is ostensibly case head expansion by feeling how the 20 W W W. G U N S M A G A Z I N E . C O M • M A R C H 2 0 1 2