Gatling Gun Feeding Mechanisms

The Gatling Gun is interested for many reasons, and one of them is the variety of feeding mechanisms that were developed and used with it. Most firearms are designed around a single specific feeding mechanism, sometimes with variants made for two types (like mag-fed and strip-fed Hotchkiss LMGs). The Gatling was one of the very first high rate of fire guns, though, and it inspired an impressive number of inventors to develop feed systems. Let’s take a look at them all, shall we?

Hopper

The first Gatling guns used a very simple hopper to feed ammunition. It was cast into the action cover, and could be continuously topped off by the assistant gunner while the gunner aimed and fired the gun. It was simply gravity fed. To assist in loading, cartridges could be fed into the hopper from very simple purpose-made tin boxes, which held 40 rounds each. These boxes were not magazines in the modern sense, as they had no springs or followers, and were used simply to pour cartridges into the gun’s hopper.

Gatling Gun tin cartridge box
Gatling Gun tin cartridge box
Model 1862 Gatling Gun
Early 1862 Gatling with prominent hopper (gun at West Point Military Museum; photo by William Maloney)

Box Magazine

With the introduction of the 1871 Gatling, the tin cartridge boxes were replaced by a true early box magazine. Instead of being manually dumped into the hopper, the new magazine would fit and lock into the feed hopper, and included a flat spring on the side which prevented cartridges from falling out of the magazine unless it was secured in the gun, at which point the spring was lifted up and out of the way (similar to a Madsen or Johnson LMG magazine).

Early 1871 model Gatling magazine
Early 1871 model Gatling magazine

Gatling mags of this period vary in capacity and curvature, depending on the cartridge they were designed for. These magazines also included weighted followers to help push rounds into the gun, although these were not spring loaded. Feed boxes for the 1865 model had been made with followers, but still having removable lids instead of spring catches to hold in ammunition. Early guns held the magazines at a 45 degree angle off the left side of the gun:

Gatling Gun with angled magazine
Gatling Gun with angled magazine

The angled magazine was located so as to allow use of the sights, which were located centrally on the gun. In 1874 this arrangement was changed, though, and the sights were moved to the right side to allow a vertical magazine on the centerline of the gun. This reduced friction in the mag, and improved feeding.

Colt 1890 Gatling with vertical magazine
Colt 1890 Gatling with vertical magazine (photo from LittleGun.info)

Broadwell Drum

In 1872, a new type of feed device was patented by the Gatling company, named after L.M Broadwell (the employee who devised it). According to the patent, this drum consisted of twenty stacks of cartridges arrayed in a circle with the bullets pointing inwards at a central column (kind of like a Lewis or DP drum). Each stack held twenty rounds, giving the drum a total capacity of 400 rounds. At the bottom of the drum was a metal plate with a hole to allow cartridges from one stack to drop down into the gun. In actual use, drums were typically a bit smaller, with the standard being sixteen stacks of fifteen rounds each (for a total of 240 rounds).

To load it, one would set the drum upside down, and drop 15 rounds into each column, rotating the bottom plate to access them. Then the plate would be rotated to a position in between two stacks so that no cartridges could fall out, and be mounted onto the gun. The body of the drum then had to be manually indexed to line a stack of cartridges up with the hole in the bottom plate, and then rotated to the next stack when all 20 rounds were fired. It’s a bit tricky to explain, so here is a brief video on it:

As best we can tell, Broadwell drums were used primarily in Naval applications, where the unit’s weight (about 50 pounds loaded) was not particularly problematic. However, it had some definite limitations. The drum was held on the gun only by gravity, and could simply fall off if fired at too steep an elevation or depression. Additionally, feeding became less reliable at steeper angles, as gravity alone also was responsible for dropping cartridges into the gun.

Bruce Feed

The most popular feed mechanism for the Gatling in US Army service was the Bruce Feed, which you can see in use on our recent video of a reproduction 1877 Gatling. It was a feed mechanism which was easily loaded from standard 20-round ammunition boxes, and easily allowed continuous fire. The reason for this is that the Bruce device could be topped up with 20 rounds or so of ammo already in it, thus giving the loader plenty of time. Gatlings could not maintain fire while changing box magazines.

Bruce Feed on a Gatling Gun
Bruce Feed on a Gatling Gun

Early Bruce feed mechanisms were made to fit guns originally designed for box magazines, but later productions guns were made specifically for the device, as it because the standard order for the US military. It would remain the preferred feed mechanism right up to the end of the military use of the gun, including the models in .30-40 and .30-06 calibers.

Accles Drum

The Accles drum was the most complex feed system designed for the Gatling, and in theory offered the most advantages as well. It was a large donut-shaped device which held 104 rounds in a long spiral groove (much like a Chinese AK drum). A rotor inside the drum (also like the AK drum) held the cartridges in position, and as the gun was cranked the action cylinder would interact with the Accles drum rotor forcing it to turn. As the rotor turned, it would drive the cartridges around the spiral groove inside the drum body, which ended at the entrance to the gun. Thus, cartridges were positively pushed into the gun exactly as fast as it was being fired, regardless of speed or angle of elevation. You can see the full Accles feed patent here.

Drawings from the Accles drum patent
Drawings from the Accles drum patent
Model 1883 Gatling with Accles Drum
Model 1883 Gatling with Accles Drum

Unfortunately, while the Accles feed was very effective when clean, it was too fragile for the rigors of field use. It did not take much dirt to impede the rotor from turning, and a dent in the thin walls of the drum could disable it completely. The US military dropped them from use, and converted their 1883 models back to using the Bruce feed system.

However, the Accles drum was the best feed system for use at very high speeds, and it was used in experiments with electrically-powered Gatling guns both in the late 1800s and much later during development of the Vulcan cannon.

Feed Strips

The Model 1893 Gatling was introduced in the new military .30 US (aka .30-40 Krag) cartridge, and came with a feed strip system very similar to the Hotchkiss machine gun. The Army bought 18 of these guns, with the option to have them converted to Bruce Feed if the strip system was not satisfactory.

Patent drawing of a feed strip system for the Gatling
Patent drawing of a feed strip system for the Gatling

The benefit of the strip feed is that is was mechanically actuated by the gun (“Positive Feed” according to the Gatling company), because the rotating cylinder of the gun pulled in the cartridges. This allowed the gun to reliably feed at any speed and any angle of elevation, where gravity-based systems could become unreliable. The feed strips were possible to reload, but intended to be disposable.

Ultimately the feed strip system was unable to impress the Army, and in 1897 all 18 guns built with it were converted to the tried-and-true Bruce feed. You can see more diagrams of the system in the original Gatling feed strip system patent.

Stripper Clips

We don’t know much about this particular adaptation of the Gatling, but it is clearly designed to feed from 5-round infantry rifle chargers. We found it at the Paris Musee de Armee – perhaps someone can tell us more about it?

French Gatling gun with a stripper clip feed system
French Gatling gun with a stripper clip feed system