The M3 submachine gun, aka the Grease Gun, and its final iteration the M3A1 submachine gun, premiered in 1944. The intent was simple: replace the Thomspon. The Thomspon was a great gun, but it had logistical issues. Thompsons were expensive and took longer to make, and the Army needed guns now. The M3 and M3A1 simplified things.

The gun utilizes a simple open-bolt, blowback design. It famously resembled a mechanic’s tool known as a grease gun, and that’s how it earned its famous nickname. Simple is as simple does, and the design utilizes welded stamped sheet steel and a very simple mechanism. Grease guns were cheaper and faster to produce than any Thomspon. At its cheapest and simplest form, the Thompson cost the army 45 bucks a pop; the M3 cost only 15 bucks.

But what’s good for the big army might not always be good for Private Joe. Sometimes cost-cutting measures result in disaster. That being said, the M3 and M3A1 Grease Gun offered the average soldier numerous advantages over the Thomspon. So, I’ve gathered five reasons why the M3 was better for the average soldier than the Thompson was.

1) The M3 Is Lighter

The M1A1 Thompson weighed 10 pounds. That’s a hefty submachine gun, but at the time, it was a lightweight automatic weapon. Yet, the M3 came in and shaved off almost two pounds, and the M3A1 was even lighter at 7.95 pounds.

The lighter a firearm is, the easier it is for the average soldier to carry it. When you can start shaving pounds off, it’s rather nice. It allows a soldier to move more easily or to do vital tasks like carry more ammunition.

2) It’s Shorter Too

The M3A1 has a barrel length of eight inches and an overall length of 29.1 inches with the stock extended. With the stock closed, the gun is a mere 21.9 inches long. The Thompson had a 10-inch barrel and was 33.7 inches long.

The shorter design of the M3 made it a bit better for close-quarters combat. It was easier to use indoors and even easier to use in and out of vehicles. The collapsing stock offered a big advantage to those in tanks and other fighting vehicles.

3) They Slowed the Fire Rate Down

The Thompson M1A1 spat 600 to 700 rounds per minute, so it was easy to quickly and inaccurately empty a magazine as the faster the firing rate, the harder the gun is to control. The Army knew this and wisely designed the M3 and M3Aq to accommodate a slower 450 rounds per minute firing rate.

This allowed the individual G.I. to have more control over the length of his bursts. A slower firing rate helps make the gun more controllable and reduces muzzle rise and recoil. Cooking off two to three round bursts was very simple with the M3A1 and M3 SMGs.

4) Easier to Reload

The Thompson had a rather annoying method of reloading. Most of us are familiar with the AR-type shove and forget or the AK-type rock and roll. On the other hand, the Thompson required users to align the magazine with an external guide to get the magazine into place. They could not reload without aligning the magazine just right with this slot.

This made reloading the Thompson a hassle, especially at night when you couldn’t see the guide. The M3 did away with that slot and simplified the reloading process. Jam the magazine in the well and call it a day!

5) It’s Simpler

The M3’s simpler design was also a benefit to Private Joe. The Grease Guns were easy to clean and take apart. The lack of wood meant nothing could swell or fail. In the field, simple is good, and the M3 and M3A1 were as simple as you can get.

The M3 and Staying Power

The original M3s certainly had some problems, and the Army was quick to recognize and rectify them. Numerous issues the gun faced included the cocking handle, which was later just removed entirely. This lead to the improved M3A1 design.

The M3A1 stuck around throughout World War II and Korea, and in the 1970s became the choice of Delta Force. Delta was fond of how quiet the gun was when equipped with a suppressor. While it served with the unit for only a short period, the gun stayed with the Army up until the 1990s and was still used by tankers in the Gulf War.

The M3A1 was a very robust submachine gun that provided a short and compact option for specialized roles. It served far longer than the Thompson, and while it wasn’t as fancy, it was more efficient. The M3A1 is oft-forgotten and lives in the shadow of its old brother, but it was a fantastic firearm for its time.