Oh, I read it as with a scope. Oops. W/o I would try 80 yards. Most shotguns don't have a rear sight and it's hard to be consistent. If you practiced a lot at 100 yards you may be able to be consistent but I would stick to 50-80 yard range. Try it at the range first to see how well you do and what groups nice. Save up and get a rifled barrel with a built in scope mount. They are worth it.