The constriction on the factory Ultifull is 695. The reason you cant find tubes that tight for this gun are because they dont make them. The 835 is not like any other 12 gauge. The end of the barrel (last 5 inches or so) is over bored. If you look it is actually bell shaped. The end of the barrel is the same width as a 10 gauge. Mossberg did this to help it pattern good. My wife has an 835and she shoots that same choke with Winchester Supreme 3.5" No. 5's. It patterns great. Try some different shells. Also, those tubes are for lead only, so dont shoot Hevishot. Good luck.