Since the first article received a fairly enthusiastic response, I have decided to continue the series on unusual firearms feeding mechanisms. Many of the devices I will cover are associated with equally interesting firearms, but for the sake of brevity I will be mostly talking about the magazines themselves. One of the more unique and important designs is the Hill H15 submachine gun, which used a transversely mounted magazine of a design that would reappear with the successful FN P90 PDW/SMG. Matt at the Historical Firearms blog writes:

Developed by engineer and inventor John L. Hill the Hill H15 submachine gun was decades ahead of its time. Hillbegan developing the idea for his futuristic looking gun in the late 1940s but it wasn’t until the early 1960s that he built his first prototypes.

The H15 feeds from unique clear plastic single or double stack magazines which were loaded into the top of the receiver. This magazine was preloaded and sealed with an aluminium cap and magazine capacity varied with length. The H15 was chambered in 9x19mm and .380 ACP and was intended to be fired as a pistol. Its rate of fire was approximately 400-500 rpm making it quite controllable. It did not have a semi-automatic capability and had very few controls with a non-reciprocating charging handle and an unusual ambidextrous crossbolt safety with the safe position in the centre.

Hill’s patent for ‘Gun with ejection through hand grip’ shows how the magazine interfaces with the ‘transfer disk’ which positions the cartridge ready for the bolt to chamber and subsequently eject. (source)

The visual similarities to the FN P90 are obvious. They both utilise a horizontal, longitudinally mounted feeding system. The main difference being that a ‘transfer disk’ or ‘turntable’ feeding system (seen in images #5 & #6) is incorporated into the action of the H15 rather than the magazine as with the P90, which has a spiral feed ramp rather than the ‘turntable’. Another shared characteristic is the weapons’ ejection, both drop spent cases from the bottom of receiver through the grip. These similarities are more than coincidence however, Hill was invited to the FNfactory in Liege in 1963 and a prototype of Hill’s submachine gun was left with FN for a number of years and was no doubt photographed and examined before being returned. It is very likely that design cues if not specifics were taken from Hill’s design as two of Hill’s patents are cited in FN’s patent for the P90′s feed system.

This patent shows that Hill’s early designs also had side mounted magazines (source)

The Hill SMG is a fascinating article in its own right, and certainly deserves its own treatment; therefore, I will most likely be doing a more in-depth article on it later. This magazine design, as Matt notes above, led directly to the FN P90, and has as a result become one of the most successful non-standard magazine configurations in history.