[fabsroman]

You can, but I wouldn't. It also depends on how much you like that gun/barrel.

The biggest problem is that a full choke barrel is way too tight, and the barrel might develop a bulge near the end of the barrel where the choke is located from the ungiving steel trying to pass through it.

The second problem is that steel patterns a lot tighter than lead because it does not deform under pressure (i.e., there are less fliers out of the pattern and less dramatic effects on the pellets from wind resistance). So, you will be shooting a Xtra Full + on those ducks/geese, which isn't really good unless you are shooting them 60 yards away, and I wouldn't recommend that for a beginning waterfowler unless you have been shooting a bunch of clays.

You can probably pick up a replacement barrel with screw in chokes for the gun at a pretty decent price. I would guess it would be around $200 and maybe even $150. I know Remington makes them, and you might also want to check out Hastings. A barrel with screw in chokes will allow you to use that gun for anything you want to shoot/hunt.