I am shooting a Mossberg 500 with a Carlson's extended Full .700 choke. I can shoot steel, lead, hevi shot, or copper plated ammo through it. I patterned the gun last fall with Winchester Supreme High Velocity Turkey loads. 3" with 1 3/4 oz of #5's. Should do the trick. Only problem I see is the gun has a 28" barrel plus the 3/4" extension, and no sights, just beads. But I have shot pretty good groups with slugs in the gun before with the factory chokes.
Later,
Marcial