Simpson machine carbine

In September 1944 the Ordnance Board received a proposal for a new machine carbine from New Zealand, submitted by one W.A. Simpson. Technical sketches of the design, but no physical prototype, were sent to Cheshunt for examination and described in a subsequent report. The gun had several interesting features. It was blowback-operated with a rotating bolt, which had a separate striker and firing pin, and was chambered in .45 ACP. The breech locked open when the magazine was expended, and most interestingly the magazine apparently did not protrude from the gun - it is unclear how this was achieved, whether perhaps the magazine lay horizontally under the receiver like the Canadian XP-54 design or McLachlan gun, or by some other method.

Although the Simpson machine carbine was considered to be a novel design, the C.E.A.D. were more invested in a rival design - it is not mentioned which specific gun this was but it was noted to be "very similar in design" to the Simpson gun. I suspect that what the C.E.A.D. was referring to was an ongoing project to convert the Sten gun to the McLachlan feed. As a result, the Simpson was not given high priority and it appears that no further action was taken. Whether a functioning prototype of the Simpson gun was ever made is unknown, but certainly none ever reached Britain for trials.

Simpson submachine gun