The .45 Auto submachine gun (SMG) is an old two-handed automatic weapon that was stored in U.S. Army and National Guard armories at the time of the war. A large number of them have surfaced after these armories were breached by looters after the war, most notably the White Legs, for whom the .45 SMG has become a signature weapon.
Like most automatic weapons, the high spread of this weapon requires the shooter to be at close range for all of the rounds fired to impact on the target, though this can be negated somewhat by the recoil compensator. Additionally, the gun consumes ammunition quickly, and can eat through .45 Auto rounds at alarming speeds.
Despite these disadvantages, the .45 Auto SMG does 525 DPS with 100 Guns skill and maxed-out perks. This makes it absolutely devastating at short range with a 50-round magazine and a high rate-of-fire. Ammunition can be found in large quantities in the inventories of vendors and on White Legs storm-drummers.
Unlike most submachine guns, the .45 auto submachine gun is classified as a two-handed weapon; because of this, traveling while holding the weapon will slow the Courier's movement speed. This also causes the weapon to be holstered on the back, rather than on the hip as with other SMGs.
Although called "storm-drums," they have no drum magazine when the White Legs use them. Thus, it is more logical to think of "storm-drum" in a literal sense, a drum that makes a sound like thunder storms.
These "storm drums" are the signature weapons of the White Legs.
While aiming in third person, the weapon's stock is not held against the wielder's shoulder.
When aiming down the iron sights in first person, the Courier's index finger slightly obscures vision.
When aiming down the iron sights in first person, the rounds hit much higher than the top of the front sight.
The weapon lacks a rear sight, but has rear sight guards.
It has a very high spread, making it hard to hit enemies from medium to long ranges.
With a weight of 11 pounds, it is the heaviest sub-machine gun in the game.
Although having the same animation from previous gun reloading models, such as the Riot shotgun, there is no sound effect when the weapon jams.