Winchester Super-x 00, 3" through Benelli M2 with full choke. I have pattened them all, and this seems work the best for me. Some people that I hunt with, will only use copper plated. I have seen no advantage to them when patterning.
This load at 40 yrds, dead right there, every time. 50 yards dead, but might have to track. 60 yrds is where it starts to get risky.
One pellet in the vitals is all it takes, but should try for 3+ in vitals for clean kill.

I have shot other loads that were tighter, but this has been the most consistant for me. With some loads, I was getting string pattens, or circular patterns where there were few pellets in the center of target. This should be avoided.

I tried Winchester 00 3" through a xxx full Comp-n-Choke, in my Winchester 1300 and got all 15 pellets in a 12" circle at 40 yds. I do not hunt with this load, because that takes away the advantage of having a shotgun if you have to aim it like a rifle. But if that is what you are looking for then give it a try.