Today I assembled my new 16" LW BCM upper with a NSR 13.5 rail. Something is off center.
I can't tell if it's the rail or the barrel. When I look at it from the end, and from the top or bottom, it is definitely closer to the left side of the rail by several millimeters. It's enough that I noticed it almost immediately after finishing the build.
I am leaning toward the rail being the culprit, because when looking down the barrel from the rear of the upper, I can't see any sort of bias to the left at all. It appears perfectly straight. I did notice, however that the barrel was VERY hard to remove, much more so than previous uppers.
Two questions:
-How can I narrow the problem down to the barrel/receiver or the rail?
-Is this something that can be caused by improper torque on the barrel nut?


Reply With Quote

Bookmarks