Would someone please explain to me when you use either a roll or taper crimp on a specific bullet. I`ve been driving myself crazy trying to fugure it out.

Burch :confused:

Burch
I'm no expert on crimps,but,in general,a roll crimp is used with a correspoding cannelure in the bullet.The taper crimp needs no cannelure.
Frank

I use roll crimps on revolver and lever action rifle rounds. I use taper crimps on auto pistol reloads. All the best...
Gil

A taper crimp is mandatory when the cartridge headspaces on the mouth of the case - 45 ACP, 40 S&W, 9 MM, etc. Roll crimps are used where the bullet has a cannelure, and is mandatory in tube magazine rifles such as the M94, M336.

QuarterChoke said it all; the only things I would add is that revolvers generally use a roll crimp to prevent the bullet from moving forward under recoil which can lock up the cylinder. Also, bottleneck semi-auto pistol cases can use a roll crimp as they headspace on the shoulder. Finally, to muddy the waters a bit, there is what Lee Precision calls a "Factory Crimp", which simply squashes the neck against the bullet without bending it inwards. This was generally used on military cartridges.

Bud W