CNC MACHINED MAC 10 M10 9mm SMG BOLT ASSEMBLY For DOUBLE STACK Magazines. Replace your old factory cast Mac 10 9mm bolt assembly with this new prwecision CNC machined bolt specifically set up for double stacked magazines. Cures feed related bolt problem commonly associated with the old MAC 10 M10 9mm cast bolt assemblies Parts Sold as Replacement Parts Only for Registered Receiver Weapons. ALL NFA Rules & Regs Apply