I have the 5" Pro model in .40. The difference in accuracy between my Kimber .45 and the M&P is very noticeable. I'll check out Bar-sto. Thanks for the heads up!
Some folks were getting 4-5" groups at 15 yards with their 9s. The .40s and .45s aren't near as bad. The .45s actually are pretty good in the accuracy dept, it's mostly the 9s that have issues. S&W has changed the rifling twist but is hasn't fixed the problem. The problem is tolerance stack in the barrel fitment to the slide. Randy Lee at APEX has made a science out of it, but the cliff note version is that some guns are just too sloppy.