The M1 Carbine is a lightweight, handy weapon that is well-liked by many. One of its weakest points for many people, however, is its cartridge: The .30 Carbine caliber is regarded by some as being too weak to be a true intermediate caliber round fully capable of effective 300m fire. Still, the .30 Carbine is short, so maybe there is another caliber out there that could fit into an M1 Carbine’s action while giving it a little more punch… It turns out that during the late 1940s and early 1950s, at least one Spanish small arms designer felt the same way, and invented the gun in the Forgotten Weapons video below:

Ian does something a little odd in the video when he identifies the rifle as being “heavily influenced by the M1 Garand”, and continues to repeat that idea several times in the video. He’s not entirely wrong, but… To my eye the rifle looks much more obviously derived from the M1 Carbine, not the M1 (Garand) Rifle. There are a couple of clues to this: The general style of the action (mechanically similar to both rifles, but aesthetically much more M1 Carbine than Garand), the fire control group, and the mass on the operating rod. Interestingly, in lieu of the tappet gas system, the Mosqueton CB-51 uses a fixed piston with many turbulence-generating rings, that looks inspired by the StG-44.

You can see how similar the Mosqueton is to the M1 Carbine below:

Calling this rifle an M1 Carbine copy isn’t quite doing it justice, honestly (although it makes for a very snappy title). The rifle isn’t in truth a direct clone of anything, although it does seem to take more from the M1 Carbine than anything else. Besides the different gas system, the rifle features an odd grip safety, and a very German-looking front end, as well as stripper clip guides!

It’s worth noting that while this rifle is called “CB-51”, it’s not the only rifle called CB-51. It seems to me that maybe “CB-51” was the name of a trial or a program to which these different weapons were submitted, although that’s only speculation on my part.