I have a setup that I am looking to get a BUIS for.  I tried the Larue mount with an extra ARMS 40L I have in the parts box.  Unfortunately, the new version with the locking lever will not close properly because the ARMS protrudes too much.  I suspect other BUIS will not work either since most appear to have the screw on the same side.  I have removed the locking lever and it will then work, but I want to retain the locking lever feature.  I know the Troys rear irons fit perfectly.  What else will work?  

Have you tried turning the LaRue mount around?  That way you could avoid the locking lever being on the same side as the BUIS screw.

HTH,
~Augee

You might move the mount one rail up toward the muzzle.  With a Troy sight and the LaRue mount mounted all the way back, right next to the BUIS, the rear locking lever is tight but still closes all the way, the safety lock can be engaged.  With a KAC 300M, because of the screw on the left side of the BUIS, the rear locking lever doesn't close all the way, but enough to engage the safety lock.

Troy with LaRue 4x32 ACOG mount


KAC 300M with LaRue 4x32 ACOG mount.  You can see where the mounting screw of the 300M is preventing the rear lever from fully closing.  As mentioned, it's close enough that it's secure and the safety lock can be pushed in.  Troy's mounting screw goes in from the right side of the BUIS.



Excuse the lint

A Troy rear BUIS is what you seek.

I just tried my LT-100 on the last slot back towards the BUIS on two different AR's, one with ARMS #40L, and the other with Troy.  The rear lever can be closed in both cases, but the lock can't be fully engaged with the ARMS.

I don't normally run it near that far back as the ACOG is an 11 series, but the Troy is GTG all the way back from my measurements, confirming your previous statement.

Because of the short eye relief, I need to mount it right behind the Troy (like on another setup I have).  So obasically, my only choice is the Troy then.  Oh, well. Wanted something different.