Well a lot of info was lost so here's the 18.5" barrel M2 and it's patterns. I had to look this up again...Always referred back to OG.
Benelli M2 18.5" barrel, .660 Rhino choke
40 yards H13 #6 151 shot in a 10.25" circle (that's the distance the Tupperware top is) 73 degrees
40 yards H13 #7 181 shot in a 10.25" circle.
I use the H13 #6 shot, just because.
God Bless,
David B.