The MB47-1913 is patterned after the original milled Bulgarian receivers but with the added feature of an integrated 1913 Picatinny stock interface. These are perfect for folding stock options from Sig or SB Tactical. Personally, I really like SB’s new triangle folder. Looks boss, comfortable to shoot, and works great on the -1913. Each 1.8 pound receiver is machined from a solid 15 pound block of US sourced 4140 steel, then heat treated to an RC41 hardness. Barrel journal is reamed to .9065 post heat treat for absolute perfection. The receiver is compatible with any milled AKM parts kit or any standard, stamped AKM parts kit. Target interference between barrel and barrel journal is .001″ Absolute max would be .0015,. Measure your barrel! *Minimal fitting may be needed with the top cover & safety for the stamped receiver kits.