MakerShot Simple Loader - Double Stack Magazine Speed Loader Step 1: Select your magazine style (single stack or double stack) and # of loaders above. Step 2: Verify your pistol compatibility below. Double Stack Compatibilities: Smith & Wesson M&P 22 Full Size, M&P 22 Compact ; Walther P22, P22Q ; Sig Sauer Mosquito ; Ruger SR22