Abstract: A firearm receiver and bolt operating assembly for use in combination with a standard bolt for a semi-automatic rim-fire action of a Ruger 10/22®-pattern firearm. It includes a receiver configured to function with a reciprocating bolt and having an ejection port which does not include a bolt handle opening on a first side and an elongated charging handle slot on a second, opposite side of the receiver. A bolt closure mechanism includes a guide rod, a recoil spring on the guide rod, and an engagement member slidably mounted over the other end of the guide rod. The engagement member is received in a transverse seat of the bolt and provides a bolt handle configured to extend through the slot opposite the ejection port. The spring and rod are inwardly adjacent to the slot and laterally between the handle and the portion received in the seat of the bolt.