Save some time and go to nitros website, buy whatever gun you want, find it on their list, use the choke/shell combo they recommend, and boom you have a stone cold killer. Only thing left is verify poa/poi, and hood sights can correct that.

I have a win. 1300 that shoots 3" mega weights - 250+ pellets @ 40 yards with the choke they recommended. I haven't done a thing to change it.