there is a show called american air-gunner on sportsmans channel where they showcase these type air guns. they are incredibly powerful, and do take down big game. show comes on thursday nights on sportsman.
Got to shoot one at a rifle expo in Vegas. Gotta be close though, lots of drop. They had all sorts of weird air powered weapons. Air powered bolts-- crossbow with no bow...it did still have limbs sort of, but no string. The limbs held the spare bolts. I won a 22 cal/shot gun air rifle at that expo. Shoots mini shotgun shells. More gimmicky than practical.
A local brought in his air shotgun he got overseas, Korea I believe he said. Looked hand made and also shot 50cal with sabot rounds. Real long too. Almost like a black powder had been modified for air. Was made by Fargo?
His wasn't self cocking or use those little co2 tanks. He had to connect a paintball tank to it to refill a long tube below the barrel where a ram rod would have been stored.
He had to load these brass cartridges with shot or sabot ball rounds. Looked like a cut down rifle cartridge with no primer in it.
He was hitting targets at 200-250 YARDS with round ball.