Hey guys, I'm just back from Dave's house. First let me say that you've got me lookin about the same way your dog would if you were trying to teach him how to play the bag pipes. All these acronyms and A1, A2 stuff is kickin my ass. I don't know what a BUIS is
Travis, you are correct in that we just want to do a simple scope mount, at least to begin with. Dave has 2 ARs, one being a DPMS with removable handle, the other a Colt with non-removable handle. Neither have been altered in any way.
We went on E Bay and purchased for the DPMS a base/rail, that is about 5.5" long. (14 notch I think) It gives 1/2" rise, and I think medium height rings will give about proper height for good face fit. The front sight will definitely be up in the scope view, but if as you say it's invisible -- no prob.
For the Colt, he got a mount that attachés with a single knob/screw to the handle, with the hole provided in the center of the handle. That would put the scope a little higher, and the front sight would probably not be as much in the field of view.
I've got plenty of different standard rings to try of the three different heights, and these bases he bought are very cheap -- errrr, inexpensive. (hope they're not complete garbage).
I'm thinking he's gonna want to eventually get a different hand guard/fore grip on the DPMS, and we need to know what kind of gas block replacement to get in any case. For now do ya think we'll be able to shoot with the scope and front sight intact?
Oh and pardon me for being so stupid about these things. This dialog should help me lose the puzzled dog look.