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Old 01-23-2010, 13:51   #5
Counting Beans
Join Date: Dec 2008
Location: Boise, Idaho
Posts: 3,240
OP, You are right to be wary of the extra bulge that you find with your stock barrel. It is a limitation to case life an pressure maxes relative to some other chambers. The extra stretching does weaken brass. When I work up in small increments, I make careful measurements of the "bulge" and compare it to some reference measurements. As I stated before, I do not load hot pressures more than once. But to your original question, you can get some pretty high performance from your stock barrel - with careful practices.

I always load hot loads with Starline brass, so over time I have developed some fairly reasonable benchmarks. The largest case expansion for loads at starting pressures measure about .431 to .4315. Mid-range loads measure about .432- .433. A Buffalo Bore factory load (Starline Brass) approaches .434" max exansion. .434" seems to be at maximum pressures. When working up, I tend to level off when case expansion measures about .4335" at the very top end, but usually less. Of course, I carefully watch for other indications of excess pressure as well.

My strategy is not as rigorous as, say, the Ken Waters method, but it gives me reasonable assurances. I also don't load "off charts." I stick with published data if available. I tend to work up to published maxes and then settle on a final load that is backed off a bit from published maxes. The 10mm performs plenty well within published limits. Your results may vary, but my chronied velocities typically exceed those of published data.

As you work up during load development you'll notice a pattern in case measurements. If you load with Starline, you may consider buying some Buffalo Bore factory loads to use as a reference point. They will be at or near max pressure. This is not foolproof by any means, but it can provide a useful benchmark.

MMA10 has some fantastic insight and I have benefited from his suggestions. I suggest doing a search for posts that he's made about the Ken Waters method and any others that relate to pressures. I agree that one should not try to "iron out" any Glock smiles. Those cases should be tossed.
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