I had a hard time locating one of the pics on my computer because it had the word "the" in front of it.
These are small versions of posters on Forgotten Weapons' merchandise site. I completely forgot where Elbonia was but the name sounded
very familiar. The 4 books I bought and read cover to cover weren't enough to remind me.
The Pedersen device turned a bolt-action M1903 Springfield rifle with a port milled into the right side of the receiver into a semi-auto. It was fed from a 40-round box magazine and the small .30 caliber cartridge had about the same muzzle energy as a .380 ACP pistol.
Tom, I expect you'll be among the handful who knows why the Puckle gun fired both round and square bullets.