The Pedersen Device is an attachment developed during World War I for the M1903 Springfield rifle that allowed it to fire a short 0.30 (7.62 mm) caliber intermediate cartridge in semi-automatic mode. This wonder weapon was developed to allow infantry to dramatically increase their rate of fire while on the move, while also allowing the rifle to be used in conventional bolt action mode for long-range fire from the trenches.

Wiki page with lots more info – HERE

This very rare collectors item is up for auction, with a starting bid (or buy now?) of $23000

It does not include a magazine, so you’d have to procure one before you got to use this beauty. I’m sure anyone that would pay $23,000 for this device probably wouldn’t be shooting with it though.