I took my M2 26" out today to pattern it... and was pretty sorely disappointed.
The best pattern I got was 102 in a 10" at 40 yards with a Rob Roberts 570.  The Hevi-Choke wasn't much different.
I tried both Federal HW #7 and Hevi 13 #7.  Multiple shots with each with clean barrel.  We tried the same RR choke in my buddy's M2 (24") with a HW #7 from a different lot, and it wasn't much better.  
I'm disappointed.  I don't even know what to do next.  I'm going to call RR tomorrow and see what they have to say.
Any thoughts?