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M3 'Grease Gun', U.S.


Type Submachine Gun
Weight 3.696kg
Length, stock extended 74.5cm
Length, stock retracted 57.0cm
Barrel Length 20.32cm
Rifling 4 grooves, RH twist
Cyclic Rate 450 rounds/minute
Caliber .45ACP
In Production 1942-1944
Effective Range 50 meters
Country of Origin United States

Cheap, ugly and effective, the M3 submachine gun entered U.S. service in December of 1942 and remained in firstline service until 1960. The original M3 can be distinguished from the later M3A1 by the presence of a bolt-retracting handle. The later M3A1 replaced this feature with a crude but effective finger hole in the bolt.

The M3 submachine gun was designed, like the British Sten gun and the German MP40, as an easily manufactured, low cost, sturdy 'bullet hose'. It was developed by well-known weapons designers George Hyde and Frederick Sampson, Chief Engineer of General Motors' Inland Division. Although officially designated M3, it was almost immediately dubbed the 'Grease Gun' by the troops who used it.

Constructed mainly of stampings and pressings, with a swagged barrel the M3 was a simple, robust, and reliable weapon. Its rate of fire was deliberately set at a low 450 rounds/minute for greater control and so that the user could trigger single shots as well as sustained bursts. The main weakness of the gun lay in the magazine, which tended to jam unless it was very meticulously maintained. The problem was somewhat alleviated by the issue and use of a plastic dustcap, but the magazine itself was never improved.

As simple as it was to produce, the M3's designers felt they could do better. In December 1944, General Motors' Guide Lamp Division, the makers of the M3, came out with the M3A1 (left, click for full-sized image); an even further simplified gun. The entire retracting handle assembly was eliminated. In its place, a crude but effective finger hole in the bolt was used for retracting. The ejection port was made larger, the cover spring made stronger, and a bracket was welded at the rear and of the stock. This bracket was used as a loading tool for pushing cartridges into the magazine, a task that was previously a finger-cramping exercise for G.I.s.

Did You Know
In the early part of the Second World War, the infantry board of Fort Benning, Georgia studied the use of silencers on submachine guns. Shortly afterward, the High Standard Manufacturing Company was commissioned to equip 1000 special perforated M3 barrels with silencers for the Office of Strategic Services (OSS).

Thanks to Robert Caulkins for the following recollection and information:

At the base of the grip is a small screw-type plug that is used to seal a reservoir inside the grip containing lubrication oil. Built on to the plug is an oiler used to put drops of oil where needed. Since the gun is entirely made of stamped and machine steel, oil is a necessity for keeping the gun in good operating condition, although it could fire after some rather heavy, and dirty handling. The extendable wire stock contained no less than four convenience features. In addition to the loading assist bracket at the rear of the stock that you mention, the width of the stock was such that it fit into two groves machined into the small collar base of the barrel - thus, the stock could be used as a barrel wrench. The other two features were a threaded recess at the front of one of the stock rods that took a wire bore brush and the other rod that was cut out to take cleaning patches.

Now the Vietnam notes. First of all, the First Marine Division Recon Battalion had the M3 in its armory at Freedom Hill near Danang. The model I saw used was silenced. While the noise of the igniting rounds can be relatively well silenced, the movement f the bolt back and forth during firing can be rather disconcerting, especially in a dead quiet triple canopy jungle area. In late 1967 I was riding the pace vehicle of a large convoy heading north from Danang to Phu Bai when we were ambushed by an NVA rocket team and riflemen on the down side of the Hai Van Pass north of Danang. One of my fellow Marines threw me his M16 a he jumped up and manned the 50Cal. machine gun mounted over the cab of the truck. Aiming in the direction of the incoming fire I pulled trigger and after 3 rounds the gun jammed. [I] Threw it down into the bed of the truck and grabbed my M3A1. I fired out four 30-round magazines during the fight and never did the gun fail to operate when I needed it. From that point on I was never without the gun, although my authorized weapon was a .45 pistol. I'm enclosing a photo of me and my baby (note the flash hider) taken by a combat photographer during the battle of Hue in 1968 [this picture didn't get through properly]. I was about to run across a street intersection which was under periodic automatic weapons fire. I was seating the magazine to the receiver after which I would open the ejection port and pull the bolt to the rear. As I recall, I ran and hosed bullets at the same time. PS - I made it across the intersection. Just in case you don't know it, the M3 can be converted to fire 9mm parabellum rounds by changing out the barrel, the bolt and using a magazine adapter that allows the use of Sten Gun magazines. All done without tools.