The “United States Submachine Gun, Cal. .45, M3”, better known as the “Grease Gun” is a simple design with a rather low rate of fire, but it is still a good thing to have around in your tank or when clearing buildings.
― Heroes & Generals
With its large magazine and automatic fire, the M3 can quickly lay waste to large groups of enemies in close quarters. Weapon modifications can be used to increase rate of fire for additional killing power. Due to low accuracy and a high falloff on ranged damage, it is inadvisable to use this weapon on targets at longer ranges. The M3 is also an excellent choice for tank crewmen as a personal defense weapon, but tankers are limited to six equipment points, which means you will not be able to equip an Adjustable Wrench. Paratroopers may also find this weapon especially useful, as a submachine gun is ideal for attacking and locking down control points. And for defense, this submachine gun can provide the firepower necessary to hold off several soldiers at once.
Magazine Size: 30 rounds, if used right, are great in those tight situations.
Close Combat: Although it is not as effective as the Thompson at close range, it can hold its own against the PPD and MP34.
Accuracy: This weapon has the second best accuracy of the entry level SMG's to balance its lower rate of fire, making headshots easier.
Iron Sight: The M3's muzzle kicks up when firing in such a way that the front pin obstructs your view through the hole of the rear sight for a moment when each bullet is fired.
Slow: The rate of fire is slow. This can be a blessing in disguise though; you tend to use less ammo, and you can easily adjust your aim for the next shot.
Ranged Combat: Although it is possible to get kills at very long ranges (it helps to be able to see each round fired), it is a waste of ammo and usually takes more than 5-6 hits.