I'd take a good look at the Leatherwood CamART scopes and mounts. It's a pain to set up but once you have all of the distances dialed in, just crank the cam and shoot. Mine will put them in a 1 gallon bottle at 500 yds. I would think for a ratty tat tat gun that would be good enough. Give them a look; http://www.leatherwoodoptics.com/index-leatherwood.html
FWIW, Jim Leatherwood made the CamART scopes for the military when he was in the marines around the Viet Nam era. His scopes and mounts are improvements over those.