..really??? ....I've read reports where the fix to the upward angle issue was to lay both HG & upper receiver upside down on a flat surface to tighten them up.
That may resolve the "upward angle" issue, but it also creates a gap between the HG and upper, although slight, in my case. I think a bigger issue is the centering of the barrel, especially since the flip-up BUIS will be mounted at the end of the tube. I'm still trying to find a way around that one, thinking a cone shaped device to slip over barrel that can be tightened down somehow on the barrel to align the barrel 360 degree with the ID of the tube.
Can't say I'm too pleased with my personal overall experience, considering the purchase price of the 15" tube and the inference that it just drops right in, tighten down & it's G2G. My individual experience has differed
All the qualities of the tube are negated by the inability to use the BUIS properly, unless I want to install them on the rail portion of the upper receiver only...
I'd replace if refunded my purchase cost, but I wouldn't sell to someone else bcuz that just isn't right in my book to push the problem onto someone else.