Troy TRX Alpha Rail and Mid-Length Gas Systems

[Mossyrock]

13″ Alpha Rails with built-in sights are not compatible with Rifle length or Intermediate length gas systems.

This is what is says on both the Troy website and Brownells. What gives? I KNOW there have been lots of these rails install on BCM middies. Is that not what they are talking about when they say "intermediate length gas systems"? Which one IS the correct length for a 16" BCM Mid-Length?

[TheGut]

My buddy did it but he said he had to shave his FSB WAY down, but it worked. Troy might have started putting that on the product description because of how many problems people have encountered while trying to do it to a mid length.

[SomeOtherGuy]

13″ Alpha Rails with built-in sights are not compatible with Rifle length or Intermediate length gas systems.

This is what is says on both the Troy website and Brownells. What gives? I KNOW there have been lots of these rails install on BCM middies. Is that not what they are talking about when they say "intermediate length gas systems"? Which one IS the correct length for a 16" BCM Mid-Length?

Intermediate length is in between rifle and midlength, and AFAIK is only used by Noveske.

I believe the 13" Alpha with the integral sight is OK with a midlength gas system, but I don't have personal experience.

Most of the slimmer / higher quality tube systems have a small internal diameter, so having to use a low profile gas block or heavily shave and alter the GI block is normal.

[twd]

I just shaved my FSB on my middy last week to install a 13 inch Alpha with integral sight. TheGut is correct, it can be done, but it has to be shaved way down, especially in the forward section of the gas block. It will fit on with a fairly normal shave job, but the sight will be pressed against the block, so much so that it will bind and not open. I shaved, installed, removed and shaved again several times before I was satisfied with the fit and function. So much so, I researched some diagrams of the internals of the FSB to make sure I wasn't going too far.