An 80 year old Finnish man invented this .22 LR belt fed machine gun. It could be fake but looks legit and is plausible. Jani confirms it is real in the comments below.

Click to expand.

The approximate translation of the caption:

80-year-old hameenlinnalaisininoori developed drilling machine, the machine became a weapon, which became a speed of 420 shots per minute. suitable balance 22 caliber cartridges.

420 rounds per minute! Not bad considering it is powdered by a drill. For comparison a blowback MAC-10 machine pistol fires 9mm around at about 1,090 round/minute. It may use the blow back to reset itself after each round

A big thanks to reader illspirit for the link.

Hat Tip: Scanned image from naurunappula.com