The 43M submachine gun was developed by Pal Kiraly, based on the MKMO and MKPS series of submachine guns he had worked on for SIG in Switzerland before returning to Hungary (we would go on to make the San Cristobal carbines for the Dominican Republic after WW2). The initial version of the gun was the 1939 39M, with a 3” longer barrel and fixed buttstock. This was adopted by the Hungarian military, but only ordered in small numbers (about 600), which led the FEG factory to delay production until they could get enough other orders to economically justify tooling up. That finally happened in 1942, and in the meantime Kiraly and the factory had nearly finished the improved and shortened 43M version.
Ultimately about 13,000 39M SMGs were made from 1942 to 1944, and about 5,000 43M SMGs in 1944. At that point Allied bombing ended production, and the tooling was eventually confiscated during Russian occupation of Hungary.
Mechanically the 43M (and 39M) are lever-delayed blowback actions, firing the 9x25mm Mauser Export cartridge - the most powerful submachine gun cartridge in use at the time. The 43M stock feels very flimsy and uncomfortable, and it folds under the action of the gun. In addition, the 40-round magazine folds forward into the stock (much like the SIG MK series guns) to make it a much more compact gun to transport. Note that the 39M and 43M use different magazines!
Thanks to the Institute of Military Technology for allowing me to have access to this magnificent piece and bring it to you! Check them out at: http://www.instmiltech.com