Superpipe9 Posted June 24, 2015 Share Posted June 24, 2015 How much does the crimp effect power factor? I recently loosened my crimp very slightly and found that my PF went down from 134 to 131. I can't think of anything else that changed. 135gr bayou bullet 3.4gr titegroup 1.110 OAL Link to comment Share on other sites More sharing options...
cnote Posted June 24, 2015 Share Posted June 24, 2015 nope, another variable, unless you were cutting into the coating, which is bad in the first place Link to comment Share on other sites More sharing options...
Hi-Power Jack Posted June 24, 2015 Share Posted June 24, 2015 You may not have fired enough rounds over your chrono - you'll get variation in your PF. I usually fire 20 over the chrono, and realize that if I fired another 20 over the chrono, my PF would change. The larger the sample, the more positive you are about what your PF actually is. Link to comment Share on other sites More sharing options...
Vlad Posted June 24, 2015 Share Posted June 24, 2015 It depends. I used to think none, but recent experiments on my part plus advice from the statisticians at Western has convinced me that "it depends". Chrono some more, vary ONLY the crimp and chrono some more. I think different powders and different bullets will react differently to changes in crimp. Link to comment Share on other sites More sharing options...
bowenbuilt Posted June 27, 2015 Share Posted June 27, 2015 (edited) The roll crimp on a revolver round can have a dramatic effect on consistency. Since an auto pistol round is not "crimped" it has NO effect on the round unless you are using the auto round in a revolver and roll crimping. If you over crimp an auto round with a taper crimp die which is really swaging not crimping, it will cause all kinds of problems. If you can see a difference in an auto round chances are you are over crimping/swaging which also causes tumbling, smoking and leading. So, if you are speaking of an auto round, used in an auto pistol using a taper crimp type die there is no difference in velocity that could be related to crimping unless you are doing it wrong. The only thing holding an auto pistol round in place is the neck tension between the bullet and the case. Taper crimping has nothing to do with this aspect unless you over do it. If you over do it, it can decrease neck tension which will effect velocity and bullet stability. Edited June 27, 2015 by bowenbuilt Link to comment Share on other sites More sharing options...
peterthefish Posted June 27, 2015 Share Posted June 27, 2015 How much does the crimp effect power factor? I recently loosened my crimp very slightly and found that my PF went down from 134 to 131. I can't think of anything else that changed. 135gr bayou bullet 3.4gr titegroup 1.110 OAL Can I be the first to say, temperature? What was the temp on each day at the time you shot them (assuming ammo had time to come to ambient temp). Also take into account if it was in sun, shade, etc... Link to comment Share on other sites More sharing options...
cnote Posted June 29, 2015 Share Posted June 29, 2015 The roll crimp on a revolver round can have a dramatic effect on consistency. Since an auto pistol round is not "crimped" it has NO effect on the round unless you are using the auto round in a revolver and roll crimping. If you over crimp an auto round with a taper crimp die which is really swaging not crimping, it will cause all kinds of problems. If you can see a difference in an auto round chances are you are over crimping/swaging which also causes tumbling, smoking and leading. So, if you are speaking of an auto round, used in an auto pistol using a taper crimp type die there is no difference in velocity that could be related to crimping unless you are doing it wrong. The only thing holding an auto pistol round in place is the neck tension between the bullet and the case. Taper crimping has nothing to do with this aspect unless you over do it. If you over do it, it can decrease neck tension which will effect velocity and bullet stability. A very detailed and eloquent way of repeating what I said, and Bowen knows his stuff!! Link to comment Share on other sites More sharing options...
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