Abstract: A new and useful a semi bolt receiver assembly is provided, that configured for assembly with a rifle base that has a buttstock and pistol grip configured for semi automatic operation. The semi bolt receiver assembly includes a receiver, a bolt and carrier assembly, and a manually operable handle that is coupled with the bolt and carrier assembly in a manner that enables the bolt and carrier assembly to be manipulated by a shooter to charge the rifle (i) while the shooter is maintaining a shooting position and (ii) without removing the shooter's hand from the pistol grip. The semi bolt receiver assembly is particularly useful when configured for assembly with an AR-15 rifle base.