RIVELLING

A British term for the wrinkled appearance of some shotgun bores.

ROLL CRIMP

A method of securing a bullet into a metallic cartridge case by bending the case mouth inward. See Taper Crimp.

ROLLED CRIMP

A method of closing the mouth of a shotshell by inverting the mouth of the tube upon itself over a top wad or slug. See Folded Crimp.

ROLLING BLOCK ACTION

A single shot action in which a breech block and hammer rotate about separate transverse pins in the receiver. The two members are swung rearward, away from the barrel breech to load the chamber or extract a cartridge case. To fire a cartridge, the breech block is closed and locking is accomplished by the falling hammer engaging an abutment under the breech block.

ROTARY MAGAZINE

A form of magazine in which the cartridges are arranged about a central rotating spindle or carrier. See Mannlicher Magazine.

ROUND

One complete small arms cartridge.

ROUND BUTT

A design of a handgun backstrap in which the lower portion features a rounded profile.

RUPTURE

A generally circumferential separation in the side wall of a cartridge case. May be complete or partial.