Just swap this drop in conversion with the bolt carrier group from your 5.56/.223 chambered rifle and you will be ready to shoot .22LR. Ships with 3 10rd magazines. For best performance use a round style hammer as notched hammers can cause function issues and 36 grain plated nose bullets have proven to be the best choice for function. – All Stainless Steel Construction includes 3 10rd Magazines. – Works in most 5.56/.223 chambered rifles.