June 11, 2015
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Jim F. asks:
What would be the pro’s vs con’s on crimping for a single shot break barrel?
Crimping can hurt accuracy because the crimp will vary from cartridge to cartridge. It’s important to have a good grip (neck tension) to properly ignite the powder charge. So there are certain instances where crimping is beneficial. As an example, we do suggest crimping our .308 cal 110gr and 130gr TSX and TTSX bullets to improve neck tension. They have such little shank to be gripped by the case that adding a crimp seems to improve accuracy.
Crimping is primarily designed to hold bullets in place, and in a single shot rifle there is no need for this application – except to improve neck tension in those rare circumstances.
There is a scenario where semi auto rifles and pistols slam the rounds into the chamber and crimping is required to hold them in place to keep them from pushing deeper in the case as they feed into the chamber, or push deeper from impacting the magazine under recoil – and also to keep them from pulling themselves as they come to an abrupt halt as they stop in the chamber. I was working with a 450 Bushmaster and found that every time I chambered a round, the bullet actually pulled itself significantly. After chambering the same cartridge a few times, the cartridge overall length grew so much that the bullet began to jam into the rifling and this is not desirable.