The Firing Line Forums - View Single Post - Rolled crimp? Taper crimp? Factory crimp? Whats the difference?

Shoney · August 11, 2009, 11:18 PM

Crimp - The compressing or turning in of the case mouth, usually into a cannelure (crimping groove) in the bullet's circumference, to provide a firmer grip on the bullet. The object is to prevent the bullet extruding from the case neck during recoil, or from being shoved deeper into the case by contact with the front wall of the magazine during recoil. With shotshells the term usually applies to the closure at the case mouth. Also the crimping of the primer pocket around the primer to seal it.

CRIMP, PRIMER - A forcing inward of the brass around the top of the primer pocket. This is frequently found on military cartridges and is done to prevent set-back of primers. The crimp must be removed before repriming the case.

CRIMP, ROLLED – For Revolver cartridges it is the constriction of the mouth of the cartridge into a cannelure on jacketed bullets or a crimping grove on lead bullets, and is to prevent the bullet extruding from the case neck during recoil. It keeps the bullet from moving The closure of the mouth of a shotshell by inverting the mouth of the tube over a top wad or slug.

CRIMP, STAR - A type of closure of the mouth of a metallic case or shotshell in which the sidewalls are folded in a star-shaped pattern. Also called Rose Crimp or Pie Crimp.

CRIMP, TAPER = is used on straight wall semi-auto pistol that headspace off the mouth of the case, and on some straight wall rifle cartridges. It is narrowing of the case along the sidewall of the bullet at the mouth of the case The pressure from the narrowed case keeps the bullet from being shoved deeper into the case by contact with the front wall of the magazine during recoil.

August 11, 2009, 11:18 PM	#4
Shoney Senior Member Join Date: February 21, 2002 Location: Transplanted from Montana Posts: 2,311	Crimp - The compressing or turning in of the case mouth, usually into a cannelure (crimping groove) in the bullet's circumference, to provide a firmer grip on the bullet. The object is to prevent the bullet extruding from the case neck during recoil, or from being shoved deeper into the case by contact with the front wall of the magazine during recoil. With shotshells the term usually applies to the closure at the case mouth. Also the crimping of the primer pocket around the primer to seal it. CRIMP, PRIMER - A forcing inward of the brass around the top of the primer pocket. This is frequently found on military cartridges and is done to prevent set-back of primers. The crimp must be removed before repriming the case. CRIMP, ROLLED – For Revolver cartridges it is the constriction of the mouth of the cartridge into a cannelure on jacketed bullets or a crimping grove on lead bullets, and is to prevent the bullet extruding from the case neck during recoil. It keeps the bullet from moving The closure of the mouth of a shotshell by inverting the mouth of the tube over a top wad or slug. CRIMP, STAR - A type of closure of the mouth of a metallic case or shotshell in which the sidewalls are folded in a star-shaped pattern. Also called Rose Crimp or Pie Crimp. CRIMP, TAPER = is used on straight wall semi-auto pistol that headspace off the mouth of the case, and on some straight wall rifle cartridges. It is narrowing of the case along the sidewall of the bullet at the mouth of the case The pressure from the narrowed case keeps the bullet from being shoved deeper into the case by contact with the front wall of the magazine during recoil.