LAGE MFG MAX-31A mk2 User manual

Owners Manual
MAX-31A mk2 Upper Receiver
LAGE Manufacturing, L.L.C. 916 E. Baseline Rd. Mesa AZ 85204 CM11-420, Rev.-

NFA Warning
This upper receiver is designed to be used with the SWD M-11A1 and RPB
M-11A1 .380 ACP submachine gun. NFA (National Firearms Act, Title 26,
United States Code) rules apply to its use and possession.
It is the owners/users responsibility to comply with all local, State and
Federal laws and regulations in the use of this product.
Copyright © 2014 by LAGE Manufacturing, L.L.C. All rights reserved. No portion of
this manual or any artwork contained herein may be reproduced in any shape or
form without the express written consent of LAGE Manufacturing, L.L.C.

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Description/Features
Features:
Length: 20-3/4”
Width: 2-1/4"
Height: 4-3/4”
Overall length with 8-1/2" stock- 28"
Weight: 3 pounds 11.7 ounces
1) Scope/Optics rail 16"
2) Cocking Handle (non-reciprocating)
3) Lower Accessory Rail 5-1/4"
4) Side Accessory Rail Mounting Points
5) 8-3/8 inch barrel length, removeable
(threaded 1/2-28)
6) Flash Suppressor
7) Mag catch
8) Trigger guard filler
(contains mag' catch and
mag' catch spring)
The MAX-31A mk2 Upper Receiver is designed to provide additional
capability to the M-11A1 submachinegun. Utilizing a heavy bolt and
longer bolt stroke, the rate of fire is reduced to around 770 rounds per
minute. This allows easy controllability of fire and the ability to consistently
fire single and two round bursts from the automatic setting.
The MAX-31A mk2 is designed to use Suomi M31 72 round drum and 50
round coffin magazines.
The MAX-31A mk2 will not function with the 36 round stick mag's which are
double feed.
The MAX-31A mk2 does not include removeable sights, scope or optics.
The MAX-31A mk2 attaches to the stock M-11A1 lower receiver without
any modification to the lower receiver.

Installation
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Insure firearm is unloaded. Point in a safe direction.
Remove magazine and pull bolt to the rear to insure
chamber is empty.
While holding cocking knob, pull trigger and ease bolt
forward into closed position.
Remove front pushpin and detach upper receiver from
lower receiver.

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Align retaining pin hole and install retaining pin.
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Make sure selector is set to "SMG". This drops the trip down
and makes it easier to install the upper. Hold upper
receiver with muzzle pointing down to prevent bolt
assembly from sliding out. Pull and hold trigger back while
installing the upper. Install upper by aligning the rear of
the upper receiver with the rear of the lower receiver,
keeping both receivers parallel. As you slide the upper
into the lower pay careful attention to not push the front
of the lower receiver into the trigger guard filler of the
upper receiver, or you may scratch the finish on your lower
receiver. If receiver will not install all of the way forward,
wiggle receiver up and down until it moves forward.

Operation
Use only full power 9mm ammunition such as Winchester
White Box 115 gr. Round Nose ammunition.
Using weak ammo will result in short uncontrolled bursts of
3 to 5 rounds. If you are unsure of your ammunition, only
load 10 rounds in the magazine and test to see if it
continues to shoot after releasing the trigger.
Do not use steel cased ammo in the 50 round Suomi coffin
magazines. The increased friction of the steel cases will
cause feed jams. Steel cased ammo will work fine in the
drum magazines.
Removal
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Point firearm in a safe direction and ensure it is unloaded
and magazine is removed.
Hold gun with muzzle pointing down and remove retaining
pin.
Pull lower receiver back about an 1/8", then pull trigger
and hold. While holding trigger back, pull lower receiver
downward and back to remove.
Recommended ammunition:

Extra magazines can be purchased from:
Vegas Drums
702-763-1269 Sales
702-706-4GUN Information
[email protected]
Centerfire Systems
102 Fieldview Dr.
Versailles, KY 40383
www.centerfiresystems.com
1-800-950-1231
Due to vartiations in magazines, some magazines may be
a snug fit but most will fit loosely. The magazine may have
a lot of play after installation, but this will not affect
functioning of the MAX-31A mk2.
Cock gun first before installing magazine.
Insert loaded magazine into mag well.
Load magazine:
Rate of fire is dependent upon ammunition being used.
"Hotter" ammo will run faster and weaker ammo will run
slower. Winchester White Box ammo will run at
approximately 770 RPM.

Note:
Cocking assembly may slightly bind when first used. With
use and lubrication, it will feel smoother.
If gun jams with the bolt forced closed, do not force the
cocking knob or hit it with a hammer. Remove upper
receiver from lower receiver. Use a screw driver to to
depress the rear of the extractor and release the case rim.
Remove the bolt assembly, then use a cleaning rod or
dowel from the muzzle end to tap the bullet out.
Pull cocking knob to rear and release. Bolt will remain
open.
Cocking knob has a spring return and will return forward
after release.
Cocking knob is non-reciprocating and will remain forward
when firing.
Cocking
Centerfire Systems
Part Number #M31DRUM
Condition of magazines- magazines are of varying quality
due to the fact that they are surplus military magazines.
Steel surface may show pitting, wear marks or light
scratches. Magazine is coated with grease. Make sure
you clean the inside thoroughly before loading.
Recommended source for magazines:

A full length rail for mounting a scope or other aiming
device is located on the top of the upper receiver. The rail
profile is compatible with most scope mounts, however,
square shaped recoil lugs may not work. These are
typically found on quick detach, throw lever mounts such
as LaRue Tactical mounts. UTG quick detach mounts are
compatible as well as others. When installing a mount, do
not force it or you may damage the upper receiver
accessory rail.
Scope/Optics Rail
A rail for attaching a front hand grip, laser aiming device,
tactical flashight or other device is attached to the
bottom of the front handgrip. Please note, some hand
grips are not manufactured to the correct dimensions to
mount on a Mil-Std-1913 rail. Ensure the grip is correct
before attaching. Additionally, tactical flashlights
designed for use with pistol accessory rails will fit on the
accessory rail but will be a tighter fit. If the item you are
going to install needs to slide on from the front,you can
remove the two screws that hold the front cover on, pull it
forward and rotate it out of the way. You can then slide
on your grip, laser, light, etc. and re-install the front cover.
Make sure you use Blue Loctite to secure the threads.
Lower Accessory Rail

The MAX-31A mk2 can be fitted with left and right side
accessory rails for mounting additional accessories. They
are installed by using the threaded holes on the sidesof
the foregrip. Screw threads are #10-32. When installing
the screws, use Loctite 242 on the threads and be careful
not to overtighten the screws.
Side Accessory Rails (optional)
Attachment of other muzzle devices
The barrel is threaded 1/2-28. The flash suppressor is
torqued to 25 foot/pounds and secured with Loctite
Threadlocker 242 A lockwasher is intentionally not used in
order to ensure the mounting surface of the barrel remains
square and burr free for optional use with a suppressor. If
you choose to replace the flash suppressor with another
type of muzzle device, insure it is designed for use with
9mm caliber bullets.
To prevent marring of the finish, apply masking tape to the
flats on the barrel end and the flash suppressor. To
remove the flash suppressor, attach a ¾" open end
wrench to the wrench flats on the barrel. Attach a
second ¾" open end wrench to the wrench flats on the
flash suppressor. While holding the wrench attached to
the barrel stationary, rotate the wrench attached to the
flash suppressor counter-clockwise.

The barrel has been designed to allow easy removal and
installation. There are ¾" wrench flats at the muzzle end.
To prevent marring the finish of the upper receiver use a
padded vise or hard wood inserts. Clamp the front sides
of the upper behind the front cover mounting screws.
Using a 3/4" open end wrench on the wrench flats at the
muzzle end, turn the wrench counter clockwise to loosen
Removal of Barrel
A sound suppressor may be attached to the MAX-31A mk2
by removing the flash suppressor. The threads on the
MAX-31A mk2 barrel are 1/2-28. A thread adapter can be
used to couple suppressors with other thread sizes or
mounting systems. Most commonly, a 1/2-28 to 3/4-10
thread adapter is required to use the suppressor that mates
to the stock M-11A1. When using the suppressor with the
thread adapter, regularly tighten the suppressor to the
thread adapter. It will have a tendency to loosen during
firing. This is typical of the 3/4-10 mounting thread and is
not related to the design of the MAX-31A upper receiver.
The recommended supplier for thread adapters is TROS
USA. Remove the flash suppressor per the above
procedure and install the thread adapter per the
manufacturers’ instructions.
CAUTION: Due to the possible variance in the
concentricity and squareness of the combined barrel,
thread adapter and suppressor you will be using, it is
recommended that thread adapters be installed by a
qualified gunsmith and the mounted suppressor be
inspected for alignment prior to firing. Additionally, some
suppressor manufacturers warranties expressly require that
they thread the barrel for the firearm that their suppressor
will be used on. The warranty for the MAX-31A mk2 Slowfire
Upper Receiver applies only to the upper receiver
assembly and not any accessories subsequently attached
by the Customer.
Attachment of a Sound Suppressor

and remove the barrel. The trunnion will come loose after
removal of the barrel. To prevent loss or misplacement of
the trunnion, insert a 10-32 screw into the accessory rail
hole to keep trunnion in place after the barrel has been
loosened and removed from the vice.
To re-install barrel, replace trunnion into the body, beveled
side forward with largest bevel down towards retaining pin
hole. Place a snap cap round into the extractor in the bolt
for barrel alignment. Replace bolt and use it to keep the
trunnion in place. Apply Loctite Threadlocker 242 to the
barrel threads and insert barrel into trunnion while apply-
ing pressure to the back of the recoil assembly. Hand
thread barrel and tighten by turning the wrench clock-
wise. Use a torque wrench to tighten to 40 foot/pounds.
VBS Rubber
Buffer 1 VBS Installed
Bolt
Recoil Plate Ejector Rod
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To adjust the rate of fire, the MAX-31A mk2 is designed to
use a varaible buffer system. (VBS)The VBS consists of a
buffer spacer that can be placed on the bolt assembly
between the rear of the bolt and the rubber buffer.
The following rates of fire can be achieved:
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.
Configuration:
Standard Bolt
One VBS Spacer installed
770
840
700
760
Rate of Fire with
Federal 115 gr Ammo
Rate of Fire with
Winchester 115 gr Ammo
Variable Buffer System, VBS (optional)

NOTE:The MAX-31A mk2 upper receiver halves are
secured together with screws.These are not intended to be
removed for routine maintenance and cleaning.
Cleaning and lubrication should be carried out per the
original manual provided with the M-11A1 with the follow-
ing additional requirements:
Recommended cleaning interval is after each shooting
session or 500 rounds of use.
Remove the upper receiver from the lower receiver. Slide
the bolt assembly fully rearward and remove.
Clean upper receiver with solvent. The metal finish and
polymer grips are resistant to most cleaning chemicals
including Mineral Spirits, Acetone and MEK. Inspect all
mounting screws for tightness.
Clean the cocking groove in the top rail of the upper
receiver by spraying with an aerosol gun cleaner. Add a
couple drops of gun oil to the top of the cocking assem-
bly.
Clean barrel using your preferred method.
Lightly coat all surfaces with gun oil. Wipe away any
excess oil.
Clean the bolt assembly in solvent. Brush the bolt face
and breach area with a nylon or brass brush to remove
any built-up carbon deposits. Ensure the bolt face is clean
and free of debris.
Using a fingertip, apply a thin coat of gun oil to the bolt
surfaces. Wipe away any excess oil. Add a drop of gun
oil to the recoil spring where it meets the back of the bolt.
Inspect the sear engagement surface for rounding or
burrs. Small burrs may be removed with a file. If the
Cleaning, Lubrication and Maintenance

surface is worn and preventing the sear from reliably
engaging, discontinue use and have it repaired immedi-
ately.
Lightly coat ejector rod with gun oil.
Insert the bolt assembly into the upper receiver.
Re-install upper receiver on to lower receiver.

The MAX-31A mk2 Slowfire Upper Receiver uses some parts that
are common to the original M-11A1. All replacement parts can
be purchased from LAGE Manufacturing, L.L.C. Additionally,
you can purchase the following parts from any company that
sells parts for the M-11A1:
Parts Replacement
Buffer
Back Plate
Extractor
Extractor Spring
Extractor Roll Pin
Referenced Manufacturers
Centerfire Systems
102 Fieldview Dr.
Versailles, KY 40383
www.centerfiresystems.com
1-800-950-1231
Loctite Threadlocker 242
Loctite is a trademark of Loctite Corp.
1001 Trout Brook Crossing
Rocky Hill, CT 06067
TROS USA
PO Box 680
Clackamas, OR 97015
www.trosusa.com

Warranty and Repair
WARRANTY
Note: Use of reloaded/remanufactured ammunition or
aluminum cased ammunition will void your warranty
The MAX-31A mk2 Slowfire Upper Receiver has been
manufactured in a manner to insure it is defect free and
durable. LAGE Manufacturing, L.L.C. warrants to the original
purchaser that this product is free from defects in materials and
workmanship for the period of One Year from the original date
of purchase. This warranty does not apply to damage due
directly or indirectly, to misuse, abuse, negligence or
accidental, repairs or alterations outside our facilities or to lack
of maintenance. We shall in no event be liable for death,
injuries to persons or property or for incidental, contingent,
special or consequential damages arising from the use of this
product. The above limitation of exclusion may be subject to
state law and may not apply to you.
To utilize this warranty, the MAX-31A mk2 Slowfire Upper
Receiver must be returned to us packaged in a manner to
preclude damage during transit and with shipping charges
prepaid. Proof of purchase date and a written description of
the complaint must be included. If upon inspection, the
complaint is verified, we will either repair or replace the product
at our election or we may elect to refund the purchase price if
we cannot readily and quickly provide a replacement. We will
return the repaired product at our expense, but if we determine
that there is no defect, or that the defect was a result of causes
not within the scope of this warranty, then you must bear the
cost of returning the product.
This warranty gives you specific legal rights and you may have
other rights, which vary from state to state.