I currently have a Reflex II for my Bushmaster on the RX06-10 (M-16 base) mount and it works great.  However, when I transfer it to my OLY 9MM A2 upper it will not fit.  The internal dimensions of the carry handle where the RX06-10 slips into is too tight.

I am now looking at getting a Compact ACOG w/M16 base and want to know if I am going to have the same issues?  Does anyone out there have an ACOG on an OLY A2 Upper that works or has also had this problem?

Oly's dimensions are off. Take some calipers and measure. If it ain't .500" it ain't good to go. I had the same problem a few years ago with a TA01 and Oly A2 upper. Send the upper back to Oly and tell them you want one with an internal dimension of .500". Like a Bushmaster!

I found that my Olympic Arms upper had it's hole drilled too far aft to mount a gooseneck forward carry handle mount to it.

Sounds like they get it almost right

I have the same problem with a Reflex carry handle mount in an Oly handle.  (Oly seems to have many problems with tolerances)  I coated the mount with grease and lightly tapped it in with a plastic hammer.  Their dimensions are off, but not by much.