Reason I ask is the eye relief on the ACOG TA01NSN is not much. I have it mounted with just 1 rail exposed on rear of upper. I would like a flip buis, but not sure how much space they need. I have my nose to the charging handle now, if I move the ACOG forward any more, it hinders my view. My A2 stock may have to go also to help get shoulder closer to the rifle. I feel like I'm sticking my neck out to get proper weld.

Thx,
HS

Most only take one, but there are a few that take more than one.  Below is an NSN with a KAC 600m under it.  Additionally, use of the BUIS would require ACOG removal, so don't worry about having it flipped up with the scope mounted, as it will be useless you you.

Thanks mongo001, yeah I plan to leave it down anyway. I may switch to a throw lever mount for the ACOG instead of the one it came with (TA51 I think). Was looking at an ARMS 40LSP or the Troy. Haven't decided yet.

take care,
HS

Quoted: Was looking at an ARMS 40LSP or the Troy. Haven't decided yet.

Both of those will work in the setup I have pictured.  Good luck.