Taper or roll crimp dies???

[quietmike]

I'm not sure I know the difference between the two. What are the strengths and weaknesses of each? How do you know which one you need? Thanks.

[oneokie]

Straight wall pistol cartridges require a taper crimp, so does the 30 carbine. Bottle necked and rimmed cartridges use a roll crimp, if crimped. Cartridges used in tublar feeds require a crimp. Most revolver cartridges require a crimp.
Hope this helps.

[BD]

Taper crimp dies size the mouth of the case smaller in a taper which, when properly done, increases the case tension on the bullet and also slightly imbeds the inside edge of the case mouth in the bullet. This type of crimp is primarily used to prevent the bullet being pushed deeper into the case as it's cycled through the action. Think straight walled semi-auto pistol cases like 9mm, 40 S&W, .45 acp.

Roll crimp dies actually roll the lip of the case mouth into the bullet, or into a groove in the bullet. While this may also prevent bullet set back, the primary purpose is to prevent the bullets in the cylinder or tubular magazine from "jumping" forward due to recoil from preceeding rounds.
Think heavy recoiling straight walled revolver cartridges like .357 mag, .44 mag, .45 colt, as well as straight wall rifle cartridges like the .44 Marlin and .45/70. Improperly done roll crimps can actually loosen the case tension on the bullet.

Lee handgun "factory crimp dies" are putting a taper crimp on the round while sizing the loaded round to sammi outside diameter, (in theory).

Rifle "factory crimp dies" are using a collet to swage a small ring at the case mouth into the bullet
which, when properly done, can really hold the bullet firmly without messing up the case neck tension. Think bottle neck center fire rifle cartridges, .223, 30-06 and the like. While not always necessary in a bolt action rifle, the Lee rifle factory crimp dies have proven very usefull to me in the AR-15 and in my .270 WBY mag using moly coated condoms, as well as in any bottle neck cartridge using a compressed load of slow powder.

BD

[quietmike]

Thanks for the explanation, now it makes sense.......but, I've never heard of this


While not always necessary in a bolt action rifle, the Lee rifle factory crimp dies have proven very usefull to me in the AR-15 and in my .270 WBY mag using moly coated condoms, as well as in any bottle neck cartridge using a compressed load of slow powder.

BD


I bet those are expensive....and slippery:D

[BD]

Condom being the local vernacular on Cast Boolits for those bullets afraid to go out without their copper jacket on.

BD