That is an early Volunteer carbine (later models designed by the same guy
were known as the Commando Arms Mark III (with a square rather than
round receiver) and later as the Manchester).
Early versions used the M3 grease gun magazines. The Mark V and Mark 45
used the Thompson magazines. There was a 9mm version called the Mark 9
but they seem to be had to find. They still show up at wildly inflated prices
at East Tennessee gun shows.
A few years back, I started research on Commando Arms but got
sidetracked. According to my notes:
""A central person at Volunteer Enterprises/Commando Arms was
James McCown. He worked at Spitfire in Arizona and then started
Volunteer Enterprises in Knoxville TN; Volunteer Enterprises was also
known as Commando Arms. Finally McCown went to
Manchester Arms located in Lenoir TN. The last Commando carbine
was the Commando Mark 45 by Manchester Arms.""
The original Spitfire was a tommy gun look-alike that was discontinued
because ATF decided it was "readily convertible". The Volunteer carbines
were redesigned to avoid the problems with the original Spitfire carbine.
Commando Arms also made stock kits for the US GI M1 carbine that
made the M1 Carbine sort of look like a tommy gun. Mark I had a fixed butt
stock, Mark II was stockless (but over 26" and still made a Title I rifle), and
Mark IV had a detachable buttstock. Plainfield Machine Company did sell
some of their M1 Carbine replicas in Mark II Commando Arms stocks.