data on fold crimp vs. roll crimp...

[mossbergman]

Anyone have any links to data on fold crimp vs. roll crimp? I plan to roll crimp shotshells and was wondering if roll crimping increases pressures all else being the same (gun poder ect).. thanks

[longbow]

Here are a couple of good articles by Tom Armbrust:

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

And some others:

http://www.ballisticproducts.com/bpi/articleindex/articles/rollcrimp1/RollCrimp.htm
http://www.ballisticproducts.com/Roll-Crimping-Tools/products/128/
http://ballisticproducts.wordpress.com/2012/12/14/does-a-shotshell-roll-crimp-raise-or-lower-pressures-versus-a-fold-crimp/

Longbow

[mossbergman]

awsome info... I will look through them and sure it contains the info I'm looking for. Much appreciated thank you!

[William Yanda]

BPI data shows roll crimped loads lower in pressure than fold crimped loads. Richard Lee in Modern Reloading 2nd Ed. says the loads provided with the Lee slug mold "are for use only with the modern star crimp and should not be used with roll crimped rounds." Although if I had to guess, dropping back from 34-36 grains of Herco to 25 grains might provide an adequate safety margin. Or might not.
Bill

[singleshot]

BPI data shows roll crimped loads lower in pressure than fold crimped loads. Richard Lee in Modern Reloading 2nd Ed. says the loads provided with the Lee slug mold "are for use only with the modern star crimp and should not be used with roll crimped rounds." Although if I had to guess, dropping back from 34-36 grains of Herco to 25 grains might provide an adequate safety margin. Or might not.
Bill

So if roll crimp loads have LOWER pressure than star crimp loads, why would you want to DECREASE the powder charge for a roll crimp?

[Johnch]

So if roll crimp loads have LOWER pressure than star crimp loads, why would you want to DECREASE the powder charge for a roll crimp?

Not always
I use a roll crimper for some steel shot loads

No expert as to why
But with some powders in my steel shot loads
Roll crimp produces slightly more pressure

I only load 2 loads with roll crimp because it is slow ( PITA)

John

[longbow]

I always thought roll crimp produced higher pressures but apparently not. What BPI indicates is that roll crimp is more consistent than fold crimp... my take anyway.

Roll crimp is slower for sure but for the slug shooting I have done so far most are roll crimped. Partly because I find getting the wad column just right for good fold crimp is harder with the slug and partly because I can tell they are slug loads with a glance at the cartridge.

Longbow