Question about shotgun primer

[Paul Harm]

Factory crimps are around .055 to .060 and that's what all the reloading data is based on. The resistance when a shotgun shell goes off is the weight of the wad and shot and the crimp depth resisting opening. So John, you're right, the crimp depth does make a big difference in pressures. From what I've read on primers, the Federal 209A and one CCI primer [ CCI 209M ] are " hotter " primers - all the rest are pretty close to the same and shouldn't make a difference at the low pressures we're using. On another reloading forum the guys recommend if subbing a Fed primer for a Win or such to go down 1 grain in powder. I've never done it seeing how I usually have at least 5 to 10,000 Cheddites on hand, just saying what they do. Most of my reloading data shows Win or Rem primers and I've always used Cheddites [ because they're way cheaper ] with no reservations.

[J.B. Books]

Originally Posted by Paul Harm

The resistance when a shotgun shell goes off is the weight of the wad and shot and the crimp depth resisting opening.

Anyone know or care to guess what the difference is between a once fired case and one that has been reloaded 5, 6, 7 or more times? I believe it is not very substantial but will be less. Want to help lower pressure a little bit with a star or folded crimp, reload well used hulls.

Take a look at this article about the difference crimp depth can make, there is a chart about 1/2 way down the page. The difference between .030 and .090 for the same reload was nearly a 4000 psi increase, yikes!

http://www.armbrust.acf2.org/primersubs.htm