Punt guns were absolutely for killing ducks. You load them, then put them in your little boat (called a punt), and blasted the lake surface clean when they were landing or taking off.
I hadn't heard of those before. That's some punk rawk warhammer shit right there. Wiki says:
"The original KS-23 was developed jointly by NIISpetstekhniki (MVD) and TsNIITochmash in 1971, it was accepted for use by the Soviet police in 1985.[1] The gun has a barrel length of 510 mm and an overall length of 1040 mm. The KS-23 has an underbarrel tubular magazine capable of holding three rounds, with one in the chamber giving the gun a maximum round capacity of four. The gun's effective range is 150 m."
Note - don't commit crimes in Russia.
Looks like those are legal here. Maybe that should be the next project.....