Holy
!!!! I want one of those!!!!
Actually, it reminds me of the same technique quoted by the department of the Army in TM 31-210 "Improvised Munitions Handbook", for using a normal shotgun to create an improvised grenade launching platform.
Hear me out on this one, I'm not makin this up. I took out all the measurements and specs, but you should get an idea from the picture, without actually being able to recreate one without the text.
Just imagine the throwbag there....instead of a grenade
You remove the shot, halve the powder, and put in cardboard disks and wadding. It creates enough pressure to lob the projectile platform.