Are both barrels on a Stevens 311-h full choke?

While I'm not sure about this particular model, I would say it's more likely that the barrels have different chokes. In the days before modern shotshells with plastic shotcups for ovepowder wads, it was common to bore the right barrel modified and the left barrel full choke. After the shotcup came into common use in loading shotgun shells, it became common to make the right barrel improved cylinder, and the left barrel modified, as the shotcups tend to make the gun throw a tighter pattern than if the old type fiber wads were used. If the gun was made strictly for waterfowling, it might in fact have been made with two full choke barrels, as waterfowlers tend to need a little more reach than, say, a grouse hunter. A gunsmith should be able to determine what the choke is for each barrel by measuring the diameter of the choke. Pattern testing might give you a clue, also. Hang a large piece of paper on a backstop 20 or 25 yards away. Put a 1 inch "bullseye" in the middle of it with a marker or stick on bullseye. Shoot one shot with each barrel, each at a clean target, using the circle or bullseye as an aiming point. Comparing the pattern spread will tell you if they're the same choke. The denser the pattern, the tighter the choke. .

If it is a 12 gauge it should have a full choke on the left barrel and modified on the right barrel. Take a dime and see if it will fit in the barrel. A dime will not fit in a 12 gauge full choke barrel.

If it is a 410 like mine then they are both full otherwise they would be diffetent like IMP and Mod. or Mad and Full.

My 311-h in 12 ga x 2-3/4" & 3" has a full choke barrel on the right, and a mod choke barrel on the left. Yours should be the same. Most fixed choke double-barreled shotguns larger than .410 have different chokes on the barrels, so you can shoot for the pattern you need for the range you need. If you look really closely, you will notice on the 311 series H, one of the last 311 series made, that they even regulated the barrels for different ranges, and that your full choke barrel points slightly higher than the mod choke, to center the pattern on the sight post at a longer range. Cool, huh?