Charlie says his Uzi is semi automatic, yet it shoots like a fully automatic. In addition, the Uzi is obviously the semi-auto Carbine model, with a longer barrel that is legal for civilian ownership in the U.S. It is a felony for a civilian to own a full-auto gun without having a federal license for each such gun.
After "Gramps" feeds the worm-dog a bottle of beer, he tells the animal to go off and play, while turning him to the floor. It's then that you can see the obvious arm of the puppeteer, clothed in the same cloth of the blanket "Gramps" is using.