The Avenger is an SMG of Northern Irish origin that was made during the 90's in an garage of private individual owning machine shop, somewhere near Belfast. Supposedly the loyalist paramilitary group (most likely to be the UVF ) that used the guns was eventually found by the police (RUC) after they hired an unknown air equipment company to make the suppressors for the gun, describing the product to them as some kind of an industrial muffler, and the manufacturing process was eventually connected and traced. Exact start of the gun production is unknown, but it ended in second half of 90's when the creator was captured by the police. The final number of produced guns is also not known, although it could be in few hundreds, since that some of the captured ones were stamped with serial numbers (which is very uncommon for homemade guns) exceeding 300.
The "Avenger" is a home-made submachine gun with a side folding stock that doubled as a front grip when folded, silencer and a vertical magazine insert. It is a "Square Section" gun meaning it uses a square pipe as its receiver. It is fed from Sten magazines with a square version of the bolt used in the Sterling L2A3, but does not adapt Sterling SMG magazines. The weapon is open-bolt fired, lacks a safety and is full-automatic only. The bolt is a wrap around barrel type with a forward recoil/return spring. In the rear section, there is a heavy coil spring that acts as a buffer. The ejector is replaceable with two screws. The barrel lacks rifling but this can in some cases possibly increast ballistics at close quarters. Suppressor is screwed on the barrel and is a sealed unit with a ported tube for 3/4 inches of its length and the final 1/4 is baffled.