Abstract: A small arms caliber reducing adaptor kit including a barrel liner and cartridge insert sized to be inserted into an original small arms barrel and an original cartridge chamber respectively, the barrel liner and cartridge insert having corresponding reduced bores with the bore of the cartridge insert having a nose opening for a pellet and a base opening for a primer - the kit further including a primer seating tool.

Abstract: An ammunition round for a small arms piece including a cartridge casing with a nose opening and base opening at opposite ends thereof and a casing defined internal chamber extending therebetween with the nose opening serving to snugly receive a pellet means and the base opening serving to snugly receive a primer means, the nose opening corresponding in cross-section with the original bore of the barrel of the small arms piece, the casing having an internal protruding displacement extending into the internal chamber adjacent the nose opening to provide a stop seat for the pellet means.