10-Hole Hero:
The M1A1 Barrel
SECRETS OF THE THOMPSON M1A1 BARREL OF THE 10-HOLE HERO
fig. 1: Top: Barrel extension as sold by the prop store a few years ago; Bottom: Barrel extension of the "Delta" Pulse Rifle.
The Barrel of the M1A1 Thompson was modified for the screen used Pulse Rifles. In order to produce a larger muzzle flash and allow cycling of the action even with blank ammunition, the barrel needed to be outfitted with a so-called "choke". Such a choke / barrel extension was sold by Propstore at some point. The available image show that the choke was a threaded barrel extension that looks suspiciously like an M14 machine screw with a drilled hole, jacketed with a metal tube to partially cover the threading.
This seems to be the case for all Hero Pulse Rifles (with real Thompson M1A1), but the barrel extension of the 10-Hole Hero Pulse Rifle does have slight differences. On most of the other Rifles (including the extension of the Delta Pulse Rifle) it is possible that the barrel was machined down a bit where it is widening, making the barrel look like a straight tube.
The 10-Hole Hero barrel extension however seems to have been machined with a much larger chamfer, so that the tip of the barrel extension is almost conical towards the muzzle. This can be seen in a multitude of scenes, including the training scene with Ripley.
Whereas all muzzle extensions feature flattened sides, most likely to uncrew the muzzle extensions, the large chamfer on the 10-Hole Hero Pulse Rifle gives these flattened sides a drop-like appearance.
Presumably, the diameter of the M1A1 barrels had to be machined down a little bit at the front (where the front sight is located) to be the same diameter as the barrel extension (18mm) as well as shortened by a tiny bit in order to sit flush with the barrel extention and give the illusion of a single barrel.
fig. 2: Movie stills showing the conical shape of the muzzle of the 10-Hole Hero Pulse Rifle.
