Running a BUIS with no elevation?

[Hop]

I just did this last weekend. 10.3" SBR and MBUS. I'd say it depends on what you are shooting at and how far away you are. I was shooting at a D size AQT out to 400 yards. The "in the black" on those targets are ~18" high. That's a bit over 4 MOA tall at 400 yards.

The shorter sight radius on the SBR means each front sight click is going to be more than the normal 1.875 MOA @ 100 yards. I was seeing 2.5 MOA per click! Two clicks @ 400 yards will take you from the bottom edge to over the head of those AQT targets. I was seeing ~5 MOA drop going from 300 to 400 yards shooting MK 262 Mod1. If you make good hits using a center hold at 300 then move back to 400 you would need to hold over at the hat to make hits at the bottom of that target. That sight picture sucks and Tango don't give you time to dig out your sight tool!!! The blade covers the entire target. When using hold overs, the sight picture using an EOTech is MUCH better than iron sights.

If you really have that much distance to play with you will want to stretch that thing out just like I did. Forget the co-witness. You'll probably want your irons zero'd at 25 yards.

[Leftie]

I go about zeroing Troy BUIS with no elevation on the rear aperture by adjusting elevation on the front sight post and windage on the rear. I run mine at a 50/200 zero on a 16" upper, and find that hitting targets at ranges greater than the 200 yard zero is a question of hold over. I have only shot a 10.5" barrel out to around 150 with irons, and find that sight radius is the limiting factor for getting an accurate shot off onto small targets. Then again, my knowledge is limited with shorter barrel lengths.