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JJE · May 4, 2010, 06:34 PM

The Speer manuals say to crimp when:

1) The case is mostly empty, in order to promote good combustion. This applies to most 38 Spl and 357 Mag loads. For SD or hunting loads, where you are generally trying to maximize velocity, I guess you would use a firm crimp. For light target loads, it doesn't really matter if combustion is inefficient as long as the grouping is good, so I tend to use light crimps on target loads to save wear & tear on the cases, and that works out OK. Also , I shoot plated bullets for target shooting, and you aren't supposed to crimp those much - I use 1/4 turn on a Lee Factory Crimp Die.

2) When you use slow powder. By slow I believe they are referring to some of the slower magnum powders, like Lil Gun, but you would put a firm crimp on those anyway because it's a mostly empty case (see 1 above).

So: Firm crimp on high-performance SD and hunting loads, and as little crimp as you can get away with (which sometimes is no crimp at all - just remove any case mouth expansion) on light target loads.

May 4, 2010, 06:34 PM	#6
JJE Member Join Date: November 1, 2006 Location: Vancouver, WA, USA! Posts: 91	The Speer manuals say to crimp when: 1) The case is mostly empty, in order to promote good combustion. This applies to most 38 Spl and 357 Mag loads. For SD or hunting loads, where you are generally trying to maximize velocity, I guess you would use a firm crimp. For light target loads, it doesn't really matter if combustion is inefficient as long as the grouping is good, so I tend to use light crimps on target loads to save wear & tear on the cases, and that works out OK. Also , I shoot plated bullets for target shooting, and you aren't supposed to crimp those much - I use 1/4 turn on a Lee Factory Crimp Die. 2) When you use slow powder. By slow I believe they are referring to some of the slower magnum powders, like Lil Gun, but you would put a firm crimp on those anyway because it's a mostly empty case (see 1 above). So: Firm crimp on high-performance SD and hunting loads, and as little crimp as you can get away with (which sometimes is no crimp at all - just remove any case mouth expansion) on light target loads.