When people hear the term “Grease Gun”, many think of the tool that administers grease to machinery and such. For World War II nerds, we immediately picture a submachine gun. Let’s delve into the history of this slightly unusual-looking weapon.
Origins
The US Military took notice of how effective submachine guns were proving to be in Europe; namely, the German MP-40 and the British Sten. A significant portion of fighting was taking place at close range, especially in built-up areas. The firepower of the submachine gun was effective.
The US already had the Thompson submachine gun, but it was expensive and complicated to manufacture. A lot of machining went into making one. They were great weapons, but the cost and complex nature demanded that a solution be found.
Consequently, one of the requirements for the new submachine gun was that it be constructed out of sheet metal. It also had to be of .45 ACP caliber with a cyclic rate of fewer than 500 rounds per minute. It had to keep 90% of shots in a 6’x6′ target at 50 yards, and it had to fire both fully automatic and semi-automatic.
Naturally, the new SMG would be compared to the Thompson.
General Motors’ Inland Division (which made other weapons for the war effort) was tasked with designing the new weapon. Five prototypes, named the T20, were completed. Each had a conversion kit for 9mm. The prototypes were tested extensively and some issues were attributed to faulty magazines. Overall, though, the testing went well. The requirement for semi-auto fire was dropped.
The Finished Product
On 12 December 1942, the US Army adopted the Grease Gun (temporary designation T20). However, the Army’s love of complicated terminology dictated that it was designated, “United States Submachine Gun, Cal. .45, M3.”
606,694 M3s were produced by Guide Lamp from 1943 to 1945. Approximately 1,000 9mm Grease Guns were produced by Guide Lamp and delivered to the OSS in 1944.
French, Norwegian, Dutch, Italian, and Belgian resistance fighters also received the 9mm Grease Gun so that they could feed them with captured German ammunition. 9mm conversion kits were also produced by Rock Island Arsenal and Buffalo Arms Corporation. Ultimately, only a small amount of the 9mm conversation kits were produced.
The 9mm conversion kits included a 9mm barrel, replacement bolt and recoil springs, and a magazine well adapter so the Grease Gun could use 32-round Sten Gun magazines.
1,000 M3 .45 Grease Guns with integral suppressors were also requested by the OSS.
Considering its stamped, welded, riveted construction, the Grease Gun was initially intended as a low-cost weapon meant to be disposed of when it became inoperable. However, later on, parts were made to service existing weapons because they were in such high demand during WWII.
Over the course of its career, various changes were made to the M3, including a revision in the retracting pawl and a new spring of the retracting lever. A modified ejector was also among other changes made to improve the operation of the SMG. A small sheet metal guard was placed around the magazine release to prevent accidental release of the magazine. Fixes were also made to the wire stock. Newer models were designated the M3A1.
Reliability
The M3/M3A1 proves to be extremely reliable because of the loose tolerances to which it is made. It uses a fixed firing pin, which is located inside the bolt. The bolt is supported by two parallel guide rods, on which are mounted two recoil springs. This allows plenty of clearance internally in the event mud or other debris is introduced to the internals.
Various Uses
Aside from regular infantry, the M3 was issued to paratroopers, drivers, and tank crews because of its compact size.
It was appreciated in the Pacific Theater of Operations because of its reliability. The Thompson could suffer stoppages because of its complicated nature and lack of a dust cover on the action. But the Grease Gun, with its simplicity, proved more reliable.
A good friend of mine who was in the military told me that they used the Grease Gun in armored vehicles well up into the late 1980s and early 1990s.
Later Improvements
In 1944, a simplified model was introduced, designated the M3A1. This had been prompted by requests from the field. Over 15,000 were produced before the end of WWII, and more than 33,000 were produced during the Korean War.
Although the Grease Gun was intended to replace the Thompson, it was not to be; instead, it supplemented the Thompson. This was because of production delays and a late introduction of the design. The Thompson remained in production throughout WWII.
The M3 first entered combat service in late 1944, with well over 622,000 M3/M3A1 Grease Guns being produced by the conclusion of WWII.
During the Korean War, the Grease Gun was the main SMG used by US and South Korean forces. Ithaca Gun Company made another 33,000 M3A1s during the Korean War, as well as parts to repair existing M3/M3A1 submachine guns.
Beginning in 1959, the M3/M3A1 was largely withdrawn from service but was issued, as mentioned, to tank crews as late as 1997. The Grease Gun was found on every battlefield since WWII. Along with many other WWII weapons, it did see some use in Vietnam as well.
Advantages Of The M3/M3A1
Cost
The Grease Gun had some advantages over the Thompson Submachine Gun. It cost only $15 to make, versus the $45 it cost to make the Thompson (late war figures). Considering it was simpler and faster to produce, this gave the Grease Gun a marked advantage over the Thompson.
Lower Rate Of Fire
The Thompson fired at a rate of 600-700 rounds per minute, making it more difficult to control on full auto. It ate up ammunition faster. The M3, on the other hand, fired about 450 rounds per minute, which made it far easier to control during full auto fire. It fired from an open bolt.
Weight
The M3A1 weighed 7.95 pounds versus the Thompson’s 10 pounds. Those who used it liked the lighter weight, which allowed them to carry more ammunition for their weapon. It was also easier to maneuver since it weighed over two pounds less than the Thompson.
Length
The overall length of the M3A1 is 29.1 inches with stock extended, with a barrel length of eight inches. With the stock folded, the length is 21.9 inches long. It is easier to store with that folding stock and handier to maneuver overall, even with the stock extended.
Comparatively, the Thompson is 33.7 inches long, with a ten-inch long barrel.
Simpler
The M3/M3A1 is simpler to clean, disassemble, and care for in the field. It has no wood like the Thompson, which could swell or otherwise be damaged. Simple is the way to go when you’re trying to maintain a weapons system in the field.
Reloading
To insert a magazine into the Grease Gun, simply jam it into the magazine well. That’s it. By the way, the magazines held 30 rounds for the M3/M3A1.
For the Thompson, there is a guide slot that the magazine has to line up with, and then it’s inserted straight in. If the mag doesn’t line up with the guide, then the user will not be able to insert it. Trying to do this in the dark or with eyes on the enemy during combat made the process more difficult.
Delta
Amazingly, SFOD-D (Special Forces Operational Detachment – Delta) used the M3A1 in 1977 because of its quietness when suppressed. Eventually, it was replaced by H&K’s MP-5. Despite that, a few M3A1s with suppressors were still in their inventory because Delta considered them to be superior to the MP-5. If anyone would know, Delta certainly would!
Other Particulars
There is no bolt hold-open device on the Grease Gun, so when it’s empty, the bolt closes on the empty chamber. A magazine change is performed, the bolt is retracted, and it’s ready to fire again. The safety is the dust cover; when it’s open, the weapon is off safe. When closed, the weapon is on safe.
A few other neat features also exist. An oil reservoir and applicator exist in the base of the pistol grip. The applicator can be unscrewed and used to oil the weapon. The oil applicator can also be used to remove the extractor pin.
The stock can be removed and used as a wrench to unscrew the barrel. The barrel has two grooves in it, which the stock is placed into, and then it is turned.
One of the stock ends is threaded at the forward end to take a bore brush and the other is drilled out to accommodate a cleaning patch. So the stock can be used in the cleaning process extensively.
A small “L”-shaped piece of metal in the stock functions as a magazine loader, since loading the final few rounds is difficult with the bare fingers.
We can see that nothing is wasted on the Grease Gun, which has a host of ingenious features packed into it. Of interesting note is the fact that the Chinese made their own copy of the Grease Gun during the Korean War. They were chambered for both 9mm and 11mm cartridges. In Vietnam, the Navy SEALs also used the M3A1 suppressed version for clandestine operations.
Overall
The troops who used the M3/M3A1 Grease Gun loved it for its simplicity, reliability, controllability, and accuracy. The M3A1 was easier to field strip and clean than the M3, which endeared it to them even more. For close-range firepower, it was hard to beat.
The fact that it soldiered on through several more wars after WWII is a testament to the weapon’s effectiveness and durability. In fact, a version of it is still in service with the Philippine military today.
This simple, little submachine gun would give most of the current SMGs in use today a good run for their money, if not prove superior.
