I just got a big doe with my mossberg 500 smoothbore. I use my shotgun for a backup deer gun and upland hunting. The more open the choke, the better groups you will get with your gun. Improved will work fine, but if you can find a cylinder bore choke that would be better. The tighter the choke constriction the more it deforms the slug and can effect accuracy. Out to 75 yards you may see no difference but I would still use an improved choke (it's what I use). The more open the choke, the less strain it puts on your barrel too. Make sure you try different slugs, I use federal 2 3/4" rifled slugs. Always use rifled slugs in a smoothbore. Just for gooness sake, shoot the gun at different ranges to see where it hits. Slugs all shoot vastly different from brand to brand. I would start with the Winchester slugs, and then try the federals, shoot whichever one shoots best. You should have no problems with your barrel unless it is an old one made with damaskus (sp?) steel. If you can change chokes, it's not that old.

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