Smith & Wesson M&P15-22 Recoil Spring Lug. Machined from steel, this recoil spring lug is manufactured for the Smith & Wesson M&P15-22 blowback-operated rifles chambered in .22 LR. This recoil lug spring is installed into the bolt assembly and retains the rifle's guide rod to the firearm. This piece is perfect as a spare on the workbench or as an immediate replacement for a lost or damaged component for your M&P15-22 rifle.