How does a die roll crimp?

Bill in NM · March 17, 2000, 02:01 PM

I reload for a number of different calibers, most of which use a taper crimp. I do understand the difference between a roll and taper crimp. My question is, as the title asks, HOW does a die roll crimp? The diameter of the bullet is larger than the cannelure depth. It would seem that it could not push the case mouth into the cannelure with out shaving off the upper portion of the bullet. What am I missing?
Thanks!
Bill

Trigger Jerk · March 17, 2000, 06:39 PM

The cannealure, of course is of slightly less diameter than the bullet, thus allowing room for the mouth to crimp in to.

The difference between the taper crimp die and the roll crimp die: The opening at the base of the taper crimp die, starts out large (relatively speaking) and gradually narrows, simply forcing the case to squeeze the bullet.

The roll crimp die "narrows" in just a few thousands of an inch, forcing the mouth to "roll" inth the bullet. If adjusted down too far, the case will buckle.

I hope that one, my explantion makes sense, and two, that it answers your question. It sure would be a lot easier to draw you a picture.

March 17, 2000, 02:01 PM	#1
Bill in NM Member Join Date: January 21, 2000 Posts: 95	I reload for a number of different calibers, most of which use a taper crimp. I do understand the difference between a roll and taper crimp. My question is, as the title asks, HOW does a die roll crimp? The diameter of the bullet is larger than the cannelure depth. It would seem that it could not push the case mouth into the cannelure with out shaving off the upper portion of the bullet. What am I missing? Thanks! Bill

March 17, 2000, 06:39 PM	#2
Trigger Jerk Senior Member Join Date: November 22, 1999 Location: Eastern WA Posts: 136	The cannealure, of course is of slightly less diameter than the bullet, thus allowing room for the mouth to crimp in to. The difference between the taper crimp die and the roll crimp die: The opening at the base of the taper crimp die, starts out large (relatively speaking) and gradually narrows, simply forcing the case to squeeze the bullet. The roll crimp die "narrows" in just a few thousands of an inch, forcing the mouth to "roll" inth the bullet. If adjusted down too far, the case will buckle. I hope that one, my explantion makes sense, and two, that it answers your question. It sure would be a lot easier to draw you a picture.