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Lage Manufacturing

MAX-31k Upper Receiver

MAX-31k Upper Receiver #514


Backordered- Add to waiting list The MAX-31k is a shortened version of our MAX-31A mk2 for the M-11A1 subgun. Overall length with our "k" folding stock in the folded position is only 17-1/2". Rate of fire is between 650 and 700 RPM, depending on ammo used. With the addition of our K-Grip, Suomi 72 round Drum magazines can be comfortably used.


Manual Video

  • Description:
    The MAX-31k upper receiver is a shortened "k" version of our MAX-31A mk2. This makes the gun more compact and "handy". Due to the short length, it is more practical to use the Suomi M31 50 round coffin magazines rather than the 72 round drum magazines. With the addition of our K-Grip, Suomi 72rd Drum magazines can be comfortably used. Sten magazines can also be modified to work and we have DC-31 30rd magazines available for sale. The DC-31 magazine is a double column, single feed, stick magazine designed for use with guns that accept Suomi M31 magazines. The 36 round suomi double feed stick magazines are not compatible.

    Features include a 13-1/2" 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 650 or 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-31k attaches to the stock M-11A1 lower receiver without any modification to the lower receiver and uses your existing retaining pin.

    The picture above shows a MAX-31k with additional Lage Mfg. accessories that are not included with the MAX-31k 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 50 Round Coffin Magazines, modified Sten Magazines or Shockwave Technologies ZMAG-S magazines.
    • 5-3/4" barrel threaded 1/2-28 at muzzle with "Birdcage" flash suppressor. Other barrel threads available.
    • 13-1/2" 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.
    • 650 to 700 RPM rate of fire. Optional rates of fire up to 1041 RPM with use of our Variable Buffer System.
    • No modification of the magazines is required.
  • Specifications:
    • Overall dimensions of MAX-31k upper recevier:
      • Length: 16-3/8"
      • Width: 1-1/2" (2-1/4" across cocking knob)
      • Height: 4-11/16"
      • Weight: 3 pounds 4 ounces

    • Overal dimensions of the MAX-31k when assembled to an M-11A1 lower receiver with a 9-1/2" stock:
      • Overall length with 9-1/2" stock- 27-7/8"
      • Height- 6-1/2"
      • Width- 2-1/4" (2-1/4" across cocking knob)
      • Weight unloaded is 6 pounds, 7 ounces
      • Weight of loaded 50 rd Coffin Magazine: 2 pounds 2.5 ounces

    • Rate of fire:
      • Winchester White Box 115 Gr. FMJ- approximately 790 RPM
        Optional Rates of Fire with Variable Buffer System (VBS): 790 to 1040 RPM
      • Federal 115 Gr. FMJ- approximately 660 RPM
        Optional Rates of Fire with Variable Buffer System (VBS): 660 to 950 RPM
      • Blazer Brass 115 Gr. FMJ- approximately 650 RPM
        Optional Rates of Fire with Variable Buffer System (VBS): 650 to 920 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.