Magnum Research Magnum Lite Rimfire is a straight pull bolt action single shot magazine fed rifle with a patented gas system and block under the barrel that taps a small amount of gas through a orifice hole in the barrel. Featuring a stainless steel barrel w/threaded muzzle and a Picatinny rail on the receiver. *Note- This rifle is designed to shoot 40 grain and 50 grain ammo ONLY.