I tested XR 6 vs Hevi 7 3" at 17 yds and at 40. The Hevi 7 was a bit better at 40 and was better (wider) for me at 17. After lots of patterning and testing, this made up my mind. I'll stick with 7's. I am getting 279 @ 40 with the 7's and I believe it was around 235 with the XR 6s. That 17 pattern is what made up my mind.
This is a 3" shell out of a BPS with a 20.5 barrel and a Sumtoy .660 Standard Invector.