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Lage Manufacturing

MAX-31C Upper Receiver

MAX-31C Upper Receiver #531


Backordered- Add to waiting list Shortened version of the MAX-31 mk2 Slow fire upper receiver for use with the M-11/9 SMG. Uses 72 and 50 round Suomi M31 9mm magazines or DC-31 30 round stick magazines.



  • Description:
    The MAX-31C upper receiver is specifically designed to allow use of inexpensive, high capacity, 72 round Suomi M31 drum magazines, 50 round coffin magazines or DC-31 30 round stick magazines. This upper will not function with 36 round Suomi stock magazines which are double feed. The longer receiver converts the M-11/9 into a carbine sized submachinegun and provides greater control and handling.

    Features include a 15-1/2" long accessory rail on top and hard mount points for additional M1913 rails on right and left side 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-11/9 upper receiver . This reduces the rate of fire (ROF) from 1,100 RPM down to around 662 RPM. 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-31C attaches to the stock M-11/9 lower receiver without any modification to the lower receiver and uses your existing retaining pin.

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

  • Features:

    Upper Receiver Image

    • Designed for use with a M-11/9 submachinegun lower receiver.
    • Requires no modification of the lower receiver to install upper.
    • Uses Suomi 72 Round Drum Magazines, 50 round "Coffin" magazines or Shockwave Technologies 30 round ZMAG-S stick magazines.
    • 5-3/4" barrel threaded 1/2-28 at muzzle with "Birdcage" flash suppressor.
    • 15-1/2" long accessory rail along top for mounting a scope or removeable iron sights.
    • Integral 2-3/4" 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.
    • 662 RPM rate of fire. Optional 699 or 769 RPM with use of VBS. Rate of fire is approximate and depends on specific ammo being used.
    • No modification of the magazines is required.
  • Specifications:
    • Overall dimensions of MAX-31C upper recevier:
      • Length: 15-1/2"
      • Width: 1-5/8" (2-1/4" across cocking knob)
      • Height: 4-1/8"
      • Weight: 3 pounds, 6 ounces

    • Overal dimensions of the MAX-31C when assembled to an M-11/9lower receiver with a 8-1/2" stock:
      • Overall length with "k" Folding Stock- 28-1/4"
      • Height- 4-11/16"
      • Width- 1-5/8" (2-1/4" across cocking knob)
      • Weight unloaded is 5 pounds, 8.1 ounces
      • Weight of 72rd Drum Magazine: 2.1 pounds

    • Rate of fire:
      • Federal 115 Gr. FMJ- approximately 662 RPM
        Optional Rates of Fire with Variable Buffer System (VBS):
        One VBS Spacer installed- 761 RPM
        Two VBS Spacers installed- 836 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.

    Use of reloaded/re-manufactured ammo will void the warranty.