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.

[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

[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.

[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

[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

[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.

[J.B. Books]

Originally Posted by 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.

Roll crimps reduce pressure slightly but it is hard to know exactly how much in each case. Personnally I will estimate/guess 500 psi on average when using it over a fold crimp recipe. Here is article from Ballistic Products with a few side by side comparisons. As you can see it can reduce pressure by as much as 1500 psi or as little as 100 psi.

http://ballisticproducts.wordpress.c...-a-fold-crimp/

[OH Osthaus]

how much does the roll crimp actually reduce pressure by?