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Old April 10, 2010, 08:17 PM   #1
slowr1der
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Join Date: March 25, 2010
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A couple of crimping questions

So I've read that you need to crimp rounds if they are a for a pump, semi auto, or lever action. So if they aren't for one of those is there any advantage to crimping them?

My next question is will crimping them change the POI? As in if I shoot some now un-crimped will I have to re sight it in when using ones that are crimped?

My third question is how exactly do I you crimp them? I've read in the reloading manuals about it and still am not sure I get it. Do you screw the screw on top of the reloading die in until you feel it have pressure? Or what do you do? I'm just a little confused on it.
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Old April 10, 2010, 08:46 PM   #2
mongoose33
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First, I don't crimp my .223 rounds which run in my semi-auto AR. Nor do I crimp 9mm or .45ACP, which both run in semi-automatic handguns.

If you're referring to handgun semi-auto rounds, the "crimp" is actually just restraightening the casemouth expansion that allows for the easy setting of the bullet. "Crimp" in something like .45 ACP is an unfortunate bit of nomenclature; normal case tension is what holds the bullet, not the "crimp."

Since a .45 ACP round headspaces on the casemouth, not the rim, it's important to return the casemouth to "square" with a taper-crimp die. But realize that the ability of the case to hold the bullet rests with normal case tension on the bullet, not the "crimp." (In that application, I believe the word "crimp" should be replaced by a term like "casemouth expansion removal" or "debelling.")

Crimp does matter in other types of ammunition; sometimes the crimp is literally a crimping onto the bullet to maintain the bullet's seating depth, and is necessary.
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Old April 10, 2010, 10:58 PM   #3
Tom Matiska
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I wouldn't say lever or pump but say tube feed. Modern clip feeds like the BLR or 7600 are less in need of a crimp than their older cousins.

Most in need of a crimp are my wheel guns... snubbies more so..... My 19oz 44special bull dog is a more of an inertia puller than my 44MAG hand cannon.

Another reason to favor heavy crimps is if you are pushing the slow end of the powder range. My early experience with the 44 Special was complicated by a vintage Hodgdon manual that published lighter loads for H110 powder(that for good reason are not to be found in any modern manual). Slower powders need to "get going to get going" and I could only avoid squibs and get consistant performance with the heaviest of crimps.
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