I have similar results from my Benelli SBE II 26" barrrel, .655 GG choke tube. The last time I patterned, I got 190 with Hevi Magblend, 276 with Nitro Magblend, and 317 with Hevi #7s, so you can probably expect some significant differences in results depending on which load your gun likes best.
Good luck and report back what you find.