An ambidextrous receiver and bolt operating assembly for use in combination with a standard bolt for a Ruger® 10/22® rim-fire firearm action. A receiver housing is configured to function with the original Ruger® 10/22® firearm bolt and has an ejection port which is smaller than the ejection port of the original Ruger® 10/22® receiver and which does not include a bolt handle reciprocation opening. The receiver housing also includes a longitudinally extending upper guide channel and an opening at an aft end of said channel. A bolt closure mechanism is adapted to bias the original Ruger® 10/22® firearm bolt into battery and to be received in a seat of the original firearm bolt. The engagement member does not include a laterally extending bolt operating handle. An ambidextrous charging handle is positioned in the channel and has a forward portion including a hook portion adapted to retract the original firearm bolt during rearward movement of said handle. The handle has a T-shaped aft portion extending out of said opening in said receiver housing.