roll crimp
 

does anyone know if roll crimping affects pressures in a signifigant (ie dangerous) way? All other factors being equal, and the shot charge being properly spaced up to the bottom of the crimp, would a recipe given for a 6 pt star crimp perform differently if it were closed with a roll?

According to my buddy in England, a roll crimp actually will reduce the pressure a bit. He roll crimps all his big bore stuff for the old hammer guns.

Destry

Destry's right. A roll crimp will reduce pressure and velocity, but by how much and how you would offset any velocity loss, I don't know. The only thing I use a roll crimp for is blackpowder.

From Bell's article The Forgotten Tens,in the DGJ 12-1. "To see what would happen, I tried a couple variations of this load. Having the test equipment allowed me to get answers to my most frivolous of questions. By leaving out one of the 1/4 inch filler wads, I had room for a six point star crimp on the smooth brass Winchester hull. With the same 38- grain charge of SR4756 powder, the velocity increased from 1202 to1288 ft/sec. The pressure jumped from 8100 to 11,000 psi! This tell me to stick with the roll crimp in my heavy loads for the 2 7/8inch ten-guage shell"

He star crimped a brass hull? Now that's a new one on me.....

DLH

The smooth brass hull is in reference to the head of the case. " I also loaded the red plastic Winchester hulls,( with smooth brass head), with 1 5/8 ounces of lead shot." This is earlier in the article. However if you try to star crimp a brass case let me know how it turns out.

Ahhhh, that makes a lot more sense. I've seen some factory loaded brass cases that has a sort of light roll crimp and I've got one English one that's got I guess what you'd call a star crimp but it only just barely goes in a bit and doesn't fold completely over.

DLH