The MAC-10 (also known as the Ingram, after it's designer) was developed in the 60's, and was used to a limited extent in Vietnam.
Unusually most MAC-10's were made in .45 ACP calibre, rather than being chambered for the more common 9mm Parabellum cartridge (though given it's 1960's US origins, it's not too surprising!). A .380 ACP version was also produced (though it was known as the MAC-11).
The .45 round has proven very useful for silenced weapons (see also De Lisle Silent Carbine) and the MAC 10 comes with a suppressor for quiet magazine emptying fun. It looks like someone screwed a drainpipe on the end but is a well put together item of gun furniture. Possibly designed for those who want to terminate with extreme prejudice some mofo but not breach guidelines on HSE noise levels OR perhaps for those Delta teams with nervous dispositions.
About as accurate as a government prediction ... however for shoeing an entire room, its pretty effective.
Much loved by movie makers as you could fire one in each hand (if your name is Neo that is).
babe and suppressor added