Just ordered a Rock River Tactical Entry upper. It has a detachable riser that has the rear sight mounted on it and a picatinny rail forward of it. Does anyone know what height rings I will need to clear the rear sight? Would like quick detach rings.

I think the idea is to use that picatinny rail for the very short red dot sights. If you are looking to use a scope you pull the whole piece off and use the picatinny on the upper.

I have the same setup on mine and bought a Larue mount as recommended by many on this site. In the future I'll use a different manufacturers product though.

Mike

I have a 42 mm nikon. What height rings will I need off of the flat top. Been looking at the Burris Tac. model.

Pretty good comparison here

http://www.maxicon.com/guns/optics/one_piece/ar15_onepiece_mounts.htm

One piece mounts are what I reccomend and LaRue or Armalite at that but all the way down on the bottom is the rings only section.

I use the RRA one piece mount and rings. They are inexpensive, have held up very well, and return to poa/poi pretty darn well with a minimum of adjustment. Just remove your "carrying handle" and bolt on the scope. The tactical entry was my first AR and that sucker would flat shoot. My brother still has it.

Rock River one piece and the burris both look pretty good for the money. Anoyone ever tried one of the Burris P.E.P.R. mounts?