I have an old 520 with what I think is a 30 inch barrel -- I'm not sure where to measure... from the firing pin out? I am shooting 40 yards at a stationary target about 1&1/2 inches wide by 6 inches tall using a very old box of 2 &3/4 inch magnum 4 and 6 shot shells. I need more shot in the target pattern, and I would like to reach out to 50 yards or more. Will a 9 shot shell get me there or do I need a different gun with a longer barrel or maybe one with a turkey choke? or both? or all three? A longer shell? or what?