Lage Manufacturing

MAX-31A mk2 Upper Receiver

MAX-31A mk2 Upper Receiver #505


This Upper Receiver has been discontinued. Please consider our MAX-31k which is a shortened version of the MAX-31A mk2.

Slow fire upper receiver for use with the M-11A1 .380 ACP SMG. Converts the M-11A1 to 9mm and uses 72 and 50 round Suomi M31 9mm magazines.

Barrel Upgrades-

The MAX-31A mk2 comes standard with a 1/2-28 barrel thread and a flash hider installed. The optional 3/4-10 thread is the original OEM thread of the M-11/9 SMG, for use with the standard M-11/9 suppressor. Select one of these options for a different barrel thread. Only select one.

3/4-10 Barrel Uprade +$20.00

3-lug Barrel Upgrade +$104.00


Manual Video

  • Description:
    The MAX-31A mk2 upper receiver is specifically designed to allow use of inexpensive, high capacity, 72 round Suomi M31 drum magazines. The longer receiver converts the M-11A1 into a carbine sized submachinegun and provides greater control and handling. The 72 round drum magazine allows you to shoot longer between magazine changes, enabling you to save precious time during matches. Features include a 16" long accessory rail on top and hard mount points for additional M1913 rails on right and left sides of front handgrip. Bottom rail is integral. Contained within the upper receiver is a heavy weight bolt assembly with a longer length of travel than the stock M-11A1 upper recevier . This reduces the rate of fire (ROF) from 1,800 RPM with .380 ACP ammo down to around 700 RPM with 9mm ammo. Due to the reduced ROF and longer bolt travel, muzzle rise is reduced, the gun feels much smoother in operation and easily stays on target. The MAX-31A mk2 attaches to the stock M-11A1 lower receiver without any modification to the lower receiver and uses your existing retaining pin. 50 round M31 "Coffin" magazines can also be used with the MAX-31A mk2, but the 36 round double feed magazines are not compatible.

    The picture above shows a MAX-31A mk2 with additional Lage Mfg. accessories that are not included with the MAX-31A mk2 upper receiver. Registered lower receiver is not included.

  • Features:

    Upper Receiver Image

    • Designed for use with a M-11A1 .380 ACP submachinegun lower receiver.
    • Requires no modification of the lower receiver to install upper.
    • Uses Suomi 72 Round Drum Magazines and 50 round "Coffin" magazines.
    • 8-3/8" barrel threaded 1/2-28 at muzzle with "Birdcage" flash suppressor. Other barrel threads available.
    • 16" long accessory rail along top for mounting a scope or removeable iron sights.
    • Integral 5-1/4" bottom accessory rail.
    • Mounting points on left and right side of foregrip for mounting additional rails.
    • Side cocking, non-reciprocating, spring return charging handle on left side.
    • Ambidextrious "Paddle" magazine release.
    • 700 RPM rate of fire. Optional 760 RPM with use of 1 VBS. Rate of fire is with Federal 115 gr. Ammo.
    • No modification of the magazines is required.
  • Specifications:
    • Overall dimensions of MAX-31A mk2 upper recevier:
      • Length: 19"
      • Width: 1-1/2" (2-1/4" across cocking knob)
      • Height: 4-11/16"
      • Weight: 3 pounds 11.7 ounces

    • Overal dimensions of the MAX-31A mk2 when assembled to an M-11A1 lower receiver with a 8-7/8" stock:
      • Overall length with 8-7/8" stock- 27-7/8"
      • Height- 6-1/2"
      • Width- 2-1/4"
      • Weight unloaded is 5 pounds, 13.7 ounces
      • Weight of 72rd Drum Magazine: 2 pounds 2.5 ounces

    • Rate of fire:
      • Winchester White Box 115 Gr. FMJ- approximately 770 RPM
        Optional Rates of Fire with Variable Buffer System (VBS):
        One VBS Spacer installed- 840 RPM
      • Federal 115 Gr. FMJ- approximately 700 RPM
        One VBS Spacer installed- 760 RPM
      • Different bullet weights, such as 124 gr. And 147 gr. , as well as lighter or stronger
        powered ammunition, will result in slower or faster rates of fire. The rates of fire
        above are approximate. The rate of fire of your ammunition may vary.

    Steel cased ammo is not recommended. Use of reloaded/re-manufactured ammo will void the warranty.