MasterPiece Arms MPA Defender MPA30T

The MPA30T is MasterPiece Arms' semi-automatic take on the MAC-10 pattern: a straight blowback 9mm pistol with the magazine well in the grip, a top-mounted cocking handle, and an aluminum lower receiver. It is a serialized semi-auto firearm, not a registered machine gun, and it is the host most MAC-pattern aftermarket parts are actually built around today. MasterPiece Arms lists it at $540, and Classic Firearms and KYGUNCO have carried it in the $470 to $500 range.

The factory barrel is threaded 1/2x28, which is the reason the Defender ends up suppressed so often. A 9mm can screws straight on with no gunsmithing, and the blowback action is not gas-sensitive, so it eats the added back pressure without tuning. The gun ships with one 30-round polymer MPA Defender magazine, adjustable front and rear sights, and a polymer case.

The Defender is not an ergonomic gun out of the box. The grip-fed magazine, the bare rear end, and the top-cocking handle mean most owners add a rear stock or brace adapter before the gun is controllable at speed. That, plus the FRT and A.R.T. trigger systems built specifically for this receiver, is what the Defender aftermarket is mostly about.