If you have ever hear someone say, I can write my name with that “gun,” they are likely referring to the M3 or M3A1, also known as The Grease Gun. While this comment isn’t meant to be taken literally, it is meant to describe the noticeable slow rate of fire, that this fully automatic submachine produces when fired.  As someone who has had the opportunity to test fire a WWII era M3, I not only agree with this assessment, but I became an instant fan of the Grease Gun, the moment I depressed the trigger and I accurately sent a long burst of 230 grain .45 ACP FMJ ammunition downrange.

            In case you are unfamiliar with the Grease Gun, this .45 ACP caliber submachine gun was featured in the original movie, The Dirty Dozen, as well as in the two remakes of this feature film.  The fact that Grease Guns went on to serve beyond WWII, was also accurately portrayed in the hit television show Tour of Duty.  In Tour of Duty there are episodes that depict a Grease Gun being carried by an American soldier assigned to MACV SOG (Study Operations Group) in Vietnam.  Grease Guns were also reportedly utilized by U.S. Special Operations personnel during the Cold War and were also issued to certain U.S. armored units in the 1991 Gulf War.

            It’s no secret that both variants of the Grease Gun take a back seat to the Thompson Submachine Gun, as far as popularity is concerned.  After all, the M3 and M3A1 were called the Grease Gun, because these sub guns looked more like a mechanic’s tool, that was used to apply grease, than a more finely crafted Thompson Model submachine gun. The Grease Gun had a more spartan look, because it was made with all metal parts, including stamped and welded metal parts. This also resulted in a submachine gun being produced that was less expensive to manufacture and did not require the use of harder to acquire materials. The original Ordnance Department requirements for this design also stated that the submachine gun, that would be designated the M3 and later the M3A1, had to be fully automatic with a “low cyclic” rate of fire.

            When the initial attempt to develop a submachine gun called the M2 was scrubbed in 1942, the Auto Ordnance Company continued making Thompsons.  Because the effectiveness of pistol caliber submachine guns was well established during the early years of the war, the U.S. Ordnance Department continued to press for the development of a submachine gun, that met the new manufacturing requirements.  In many ways, this new design would emulate the British Sten Gun. The development of the sub gun that was designated the U.S. Submachine Gun, Caliber .45, M3 eventually occurred in 1942, with production commencing in 1943 by the Guide Lamp Division of General Motors.

            Just like the Thompson, the M3 also underwent some operating changes and modifications. One of the biggest design changes resulted in the use of a different method to retract the bolt, by replacing the lever like charging handle with an indentation/hole in the bolt assembly. This enabled the operator to use their finger to retract the bolt to the rear.

            The Grease Gun was also designed to use the hinged metal cover over the ejection port as the safety.  When the box shaped ejection port cover was lifted or raised the weapon could be fired. When the weapon needed to be placed on safe, the cover over the ejection port was lowered. 

            Even though the initial reaction was for troops to be reluctant to transition from the finely crafted Thompson, the M3 proved to be a reliable submachine gun to carry in harms way, including while serving in adverse operating conditions.  Even the slower rate of fire proved to be an asset, that enabled the operator to accurately place more rounds on target.

            The difference in weight between a loaded Grease Gun and the Thompson is another factor that must be considered, when the two designs are compared and evaluated.  An M3 that was fully loaded with a 30 round metal magazine weighed 10.17 pounds and a loaded M3A1 weighed 9.82 pounds.  In contrast, a Thompson Model 1928A1 loaded with a 30 rounds of .45 ACP ammunition weighed 12.67 pounds. Clearly, this difference in weight was a very serious consideration, for troops who often carried other items, including a supply of loaded spare 30 round magazines.

            The retractable wire stock on the M3 and M3A1 also made the Grease Gun more compact. This made the M3/M3A1 a very user friendly weapon for armored vehicle crews to carry, as opposed to a Thompson that wasn’t fitted with a removable wooden stock. A suppressed model was also developed.

            A 9mm Grease Gun was also produced during the war. The U.S. 9mm S.M.G. was specifically designed for use by Allied resistance fighters and members of the American Office of Strategic Services (OSS), who operated behind enemy lines and had access to more captured German 9mm ammunition. Several hundred kits were also manufacture that enabled a M3 chambered in .45 ACP caliber to be converted in the field, to operate with 9mm ammunition.

            By December of 1944 the continued fine tuning of the M3 resulted in the development of the M3A1. However, because just under 15, 500 M3A1s ended up seeing front line service, the actual reputation of the Grease Gun was made by the 600,000 plus M3s that were issued to troops.

            While the Thompson Sunbmachine Gun is the most famous of the WWII era U.S. pistol caliber sub guns, the M3 and M3A1 deserve equal notoriety, because the Grease Gun proved to be everything that the Ordnance Department’s required, when it decided to promote the development of a new submachine gun. It should also be noted, that the Guide Lamp Division of General Motors was ideally

suited to assume responsibility for this project, because it had experience in the manufacturing of stamped metal parts.  This is a perfect example of how a peacetime manufacturing process was easily converted to produce war material.

Reference material:

1.Weapons of the Navy SEALs By: Kevin Dockery

2. U.S. Infantry Weapons of World War II By: Bruce M. Canfeild

3. Wikipedia.

Nick Jacobellis is a Medically Retired U.S. Customs Agent and a former NY police officer who was physically disabled in the line of duty while working undercover as a federal agent. To date, the author has published over 205 magazine articles and nine action-packed nonfiction, historical fiction, and fiction books: Controlled Delivery Books One and Two, The Frontline Fugitives Books I, II, III, and IV, Buck Banderas U.S. Marshal Books One and Two and A Special Kind of Hero. These books have received 5 Star reviews and are available on (US), and (UK). The K9 Academy is the author’s 10th book. The author was born and raised in Flatbush section of Brooklyn N.Y. and has an BS Degree in Police Science from John Jay College of Criminal Justice.