08-07-2018, 01:15 AM
Never used the AT3 red dot but there's quite a few mounts on Google Images that are semi-permanently fixed to the rail with a wrench. If your red dot mount is not quick detach then you will be looking through the (broken?) red dot when you deploy the BUIS. Hopefully that works. That said, if the red dot is at the same height above the rail as the BUIS then it makes for easy zeroing. You zero with the red dot and then flip up the BUIS and adjust until they co-witness with only the need to check zero with a couple of rounds.
To be honest I used to be a big fan of solid metal Troy flip-up BUIS but you can't use them with a normal scope attached and that requires taking it off, which means the scope has failed in some way. The likelihood of that ever happening is about zero. For close-in CQB with a scope (and you don't want to, or have time to take it off) on I have heard the offset fixed sights like Dueck Defense work. I haven't used them however so cannot comment.
To be honest I used to be a big fan of solid metal Troy flip-up BUIS but you can't use them with a normal scope attached and that requires taking it off, which means the scope has failed in some way. The likelihood of that ever happening is about zero. For close-in CQB with a scope (and you don't want to, or have time to take it off) on I have heard the offset fixed sights like Dueck Defense work. I haven't used them however so cannot comment.