I tried shooting my Benelli Super Nova with slugs for the first time. What a disappointment. It was hitting SOO inconsistent. It didn't matter if I was shooting offhand or off of the bench. It would not hit the same way twice. Out of 15 rounds at 50yds, I hit an 8in target twice, once solidly, once I just caught the edge of it. Other times I was hitting more than a foot high and to the Left or Right. I was using Winchester 2 3/4 in slugs.

What am I doing wrong??
Could the type of choke I had in cause this?
Ammo type?

Normally at 50 yds with a rifle off of the bench I can put 6 rounds in an X ring.