I originally had BCM KMR Alpha rail (1.3 inner diameter) on my build that I believe the low-profile Faxon GB was vibrating against the rail giving me vertical stringing and as soon as I replaced it with a MI SP-Series (Suppressor Compatible) Rail the vertical stringing went away I am now getting good groups.
At first I thought there would be no problem because it did clear by a bit when looking at it inside the rail. When just flexing the barrel by hand it seemed to flex a lot more with the BCM KMR Alpha than it does with the larger more sturdy barrel nut of MI.
I also noticed with a couple of BCM KMR rails I used in the past it seemed that the barrel nut is made of a soft metal and marred very easy even when only torquing to 40 foot-pounds as per instructions from BCM.
When I installed the MI rail I went with Bill Alexander's advice and didn't want to torque any less than 60 foot-pounds and ended up making it to almost 80 foot-pounds when everything lined up and that seemed to do the trick.
At first I thought there would be no problem because it did clear by a bit when looking at it inside the rail. When just flexing the barrel by hand it seemed to flex a lot more with the BCM KMR Alpha than it does with the larger more sturdy barrel nut of MI.
I also noticed with a couple of BCM KMR rails I used in the past it seemed that the barrel nut is made of a soft metal and marred very easy even when only torquing to 40 foot-pounds as per instructions from BCM.
When I installed the MI rail I went with Bill Alexander's advice and didn't want to torque any less than 60 foot-pounds and ended up making it to almost 80 foot-pounds when everything lined up and that seemed to do the trick.