Grease was the Word – the M3 Gun

The M3 ‘grease gun’ was a rude, crude, effective submachine gun that saw service from the Korean War through the late 1990s.

The M3 “grease gun” was one of the simplest, ugliest, and cheapest personal weapons ever fielded by the U.S. military. But, as one U.S. Marine combat veteran recalled, what this crude submachine gun lacked in looks, it more than made up for that with brutal effectiveness.

“The first time I went to use my rifle, it went ‘click’, so I busted it over a rock and picked up a dead Marine’s grease gun,” said USMC Korean War veteran Don Campbell. “I was lethal with the grease gun. It worked really well on the enemy.” Campbell made his remarks at a machine gun shoot after firing a grease gun for the first time since he served in combat over 60 years ago.

The original M3 submachine gun was commissioned shortly before the U.S. entered World War II as a replacement for the Thompson M1928 submachine gun. The Thompson, although a popular and effective weapon, was not well suited to the demands of wartime high-volume manufacturing.

Thompson production called for skilled machinists to perform many complicated machine operations and required large quantities of high grade steel. The result was a weapon that was expensive to manufacture and slow to produce. What was needed instead was barrel, bolt, and firing mechanism.

The one-piece telescoping wire stock can be removed and used as a cleaning rod, disassembly tool and, on the later M3A1 variant, as a magazine loader.

THE GREASE GUN is a compact weapon with an overall length of 29.8 inches with the stock extended and 22.8 inches with the stock collapsed. The barrel is 8 inches long. The 8.15-pound empty weight of the gun is brought up to 10.25 pounds once a loaded magazine of 30 .45 ACP rounds is inserted.

The M3 is blowback operated and fires from an open bolt. An external cocking handle is used to retract the bolt. The weapon fires fully automatic only at a listed cyclic rate of 450 rounds per minute. The ejection port cover doubles as a safety by locking the bolt in place when closed. The 30-round box magazine is a double-column, singlefeed design based on the STEN.

Personal accounts from WWII indicate the weapon was initially greeted with skepticism by many troops who were used to the more refined Thompson and the finely made M-1 Garand. The tubular sheet-metal design led to the nicknames “grease gun” and “cake decorator,” after two common implements of the day.

The grease gun’s attributes became evident in use: The weapon’s simple construction and operation made field maintenance straightforward. The gun’s relatively slow cyclic rate allowed skilled shooters to easily fire short bursts, or even single shots, to help ensure that more of the 230-grain .45 ACP rounds found the enemy.

The design was simplified even more with the M3A1 modification. The cocking handle, which had a tendency to break in use, was removed and instead a hole was drilled in the bolt. To load the gun the soldier simply inserted his finger in the hole and pulled the bolt back by hand. This model also included several other small improvements.

With the stock closed the grease gun is more compact than the
Thompson. The ejection port cover acts as a safety so that, at least in theory, the gun can be carried with the magazine inserted, bolt retracted, and the cover closed. In practice, the gun was still known to fire if dropped and the ejection port cover was knocked open by the impact.

“I had an accidental discharge with my gun,” Campbell recalled. “I missed the members of my squad by 8 or 10 feet. After that they issued an order that I could only carry the grease gun when I was in front of the main line of resistance.”

I’VE HAD A CHANCE to fire the M3A1 grease gun on two separate occasions. At first glance the weapon’s appearance is off-putting. The metal is roughly finished and the welds can best be described as “functional.” The stamped-sheet metal trigger seems especially cheap.

Overall, the gun reminded me of vintage stamped tin toys from the same era. However, when I picked it up, I was surprised by the heft. Although the body is stamped sheet metal, the bolt is machined from a solid chunk of steel, and makes up a significant portion of the total weight.

The fixed sights are a simple rear peep and front post. They are
supposedly regulated at 100 yards, which I believe is optimistic for the .45 ACP cartridge. I found the M3A1 to be simple to operate. The ejection port cover is easy to manipulate and, while it seems weird to insert your finger in a hole in the bolt to cock the weapon, it does work. The magazine well is generous and the magazine locks in easily.

There is no selector, so if the dust cover is open, the weapon is ready to fire. The gun’s slow 450 rounds-per minute cyclic rate makes it easy to fire short two- or three-round bursts or even single shots. In fact, I found it harder to make myself hold down the trigger to fire long bursts than to fire short bursts.

I did find that longer bursts tended to go up and to the right, but since it was so easy to double-tap or triple-tap the target with short bursts, I didn’t see this as much of a problem. The slow rate of fire gives it a distinctive “feel” as it chugs along and it seemed as easy to use and accurate as any of the SMGs of that era.

By the end of WWII, more than 600,000 M3 and 15,000 M3A1 SMGs had been produced by GM’s Guide Lamp division. An additional 33,000 M3A1s were manufactured by the Ithaca Gun Company for use during the Korean War. Besides use by the U.S. military, the grease gun was provided to allies as military assistance.

The weapon saw active combat service in the Greek Civil War, Korean War, and Vietnam War, among other conflicts. The grease gun was used by the U.S. as a personal weapon for armor crewman as late as the 1990s and is still in service in some parts of the world. Not a bad record for weapon that began as a wartime expedient. 􀂐

Story and Photos by Rob Reed
Photos by John Bosio

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September 15th, 2017 by