Question about shotgun primer

[Jim Partlow]

Not sure what you meanby spacer. I will be roll crimping my
Shells using overshot card. My understanding roll crimping causes
Less pressure than a regular crimp. If I go to a 3/4 oz load
I'll add a cherio or bean to make up for the omitted 1/8 oz
of shot.

[John Taddeo]

Sorry Jim , I was referring to stand in spacers in place of a short kit when going from 2.75 to 2.5 hull length. I am surprised a .030 difference would increase pressure that much. If I am reading the chart right. (my fault .020)

[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.

[John Taddeo]

Thank you Paul, now I set up my crimping station to achieve a slight recessed as close to factory crimp as possible. When switching to shorts I am slipping the short kit plate in and having at it (still getting a nice crimp). With pressure being a little more of a concern with these loads exactly where would I be measuring from start to finish to obtain this.055 to .060. I hate to sound stupid but I don't know where this measurement is being taken. And it sure looks like it makes a difference.

Thanks much.

[10ga Hammer]

Crimp Depth Measurement

[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

[OH Osthaus]

Originally Posted by Jim Partlow

If I go to a 3/4 oz load
I'll add a cherio or bean to make up for the omitted 1/8 oz
of shot.

maybe you should go with the bean

just saying
http://parkerguns.org/forums/showthread.php?t=10750

[Jim Partlow]

Paul.... Where does a roll crimp fit into the
Pressure quotient? I have read somewhere
that roll crimps offer less resistance, thus less
Pressure. Would appreciate your input.
Thanks Jim P.

[OH Osthaus]

how much does the roll crimp actually reduce pressure by?

[Jim Partlow]

To be perfectly honest I'm not sure if a roll crimp does reduce
Pressure. I read about it somewhere, and they did not offer any
Numbers. It may have been from Ballistic products. I'll have
To check.