The Benelli CB-M2 is an experimental Italian submachine gun.
Originally designed in the 1980s, the Benelli CB-M2 was supposedly invented to use a caseless round. However, due to inefficiency and a variety of rather noticeable self-defeating aspects, it brought no sales and the project was shelved.
The CB-M2 looks like a regular submachine gun with a folding stock, but has a rather peculiar void behind the magazine well; this was an ejection port for rounds to be pulled out when a jam occurred. It is similar to a rimfire weapon, where the hammer strikes the top of the cartridge.
Unfortunately, the weapon had a few self-defeating characteristics; one of which was its potential to cook off, as normal firearms eject spent casings which act as heat sinks for the enormous amount of thermal energy released from firing. Benelli had hoped to solve this problem through its use of unique caseless ammunition by adding a long, thin brass cylinder to act as the heat sink; however, the excess brass practically added negated the use of the brass cylinder as the heat sink, along with practically defeating the main theoretical advantages of using caseless ammunition.
Yet another problem was that even though it maintained a way for a user to extract and eject live rounds from it, this made it no simpler than any submachine gun on the market at the time; in fact, the CB-M2 was arguably more complex than most.
The CB-M2 used an experimental round developed by Fiocchi Munizioni, the 9×25mm AUPO. Similar to the ubiquitous 9×19mm Parabellum in terms of ballistics, the 9mm AUPO round was advertised as caseless, but not in the context of a solid propellant body with a bullet inside, as the cartridge's "case" was permanently attached to the bullet, and left the barrel together with the bullet when firing. The powder is packed in the hollow interior behind the permanently-affixed bullet with the cartridge using a ring primer built into the casing.
- Caseless weapons had existed for a while before the CB-M2 was created; like the Daisy V/L and the Gerasimenko VAG-73. The idea of the CB-M2 was later implemented into the Lightweight Small Arms Technologies project, or LSAT.