Wonerful reply by Mac. However, the answer is to get first round hits. Don'r rely on the shot spread to hit your target. Put the entire payload in them or select slug. If you miss with a pellet, you are responsible for it. (As Louis Awerbuck says, "The bad guy's name is on the front of the pellet, yours is on the back.")
Mike Sees, the Sees Patternmaster Choke does a tremendous job as well as the Vang. We recently did tests with the Vang, Jug, Sees, Rem Choke, Sees Choke merely screwed in, and the 870 cylinder bore. The Sees job did the best, followed by Vang, the tne Sees screw in.
I would also suggest patterning your gun with the load you intend to carry and affixing it to the stock of the gun. That way, you can't forget when the pattern will exceed the sidth of your target.