The question of how many rounds in a tommy gun exists at the intersection of historical fact and technical nuance. Often visualized in the hands of 1920s gangsters or WWII infantrymen, the Thompson submachine gun, colloquially known as the tommy gun, is an icon of automatic fire. Understanding its capacity requires looking beyond the simple box magazine and into the specific models and eras of its production, as the answer is not a single number but a range defined by the weapon's design.
Defining the "Tommy Gun" and Its Magazine Types
To determine the round count, one must first define the platform. The term "tommy gun" generally refers to the Thompson submachine gun, specifically models like the M1921, M1928, and the simplified M1/M1A1. These weapons were designed to use two primary feeding systems: the iconic circular box magazine and the later, more common stick magazine. The choice of magazine directly dictated the ammunition capacity, meaning the answer to how many rounds in a tommy gun is dependent on which version you are examining.
The Iconic Circular Box Magazine
The circular box magazine is the component most associated with the tommy gun's visual identity. Mounted horizontally on the receiver, this magazine utilized a complex spiral winding system to feed ammunition. The standard issue version used by the U.S. military held 20 rounds, providing a balanced mix of firepower and manageability. However, the most famous variant was the 50-round drum magazine, a distinctive circular unit that sat atop the receiver.
Standard box magazine: 20 rounds
High-capacity drum magazine: 50 rounds
Aftermarket and commercial drums: 70–100 rounds
While the 50-round drum offered an impressive volume of fire, it came with significant drawbacks. The weight of the drum made the weapon front-heavy, and the complex follower mechanism was prone to jamming in the dirt and mud of combat. Consequently, while visually striking, the 50-round drum was often less reliable than the standard 20-round box in field conditions.
As the United States ramped up production for World War II, the Thompson was redesigned for simplicity and cost-effectiveness, resulting in the M1 and M1A1 variants. These models abandoned the expensive and fragile circular magazine in favor of a straight stick magazine, similar to that of the M1 Garand rifle. This change streamlined production but altered the capacity.
Model | Magazine Type | Round Capacity
M1928 / M1921 | Circular Box (Standard) | 20 Rounds
M1 / M1A1 | Stick Magazine | 30 Rounds
The switch to the stick magazine increased the standard capacity to 30 rounds. This 30-round stick became the new norm for military and law enforcement use during the war, offering a practical compromise between weight, reliability, and firepower. While aftermarket stick magazines existed for the older models, the 30-round count is most closely associated with the simplified M1 generation of the tommy gun.
