I have both Colt M4 flat-top, and Bushmaster carbine flat-tops.  Will the ARMS 40L sight work with the front sights on both, or at least one of them (I know the Colt has the "F" front sight tower, but I don't know how much shorter it really is than a non-F one).

Put another way, when installed on a flat-top receiver, is the aperature of the ARMS 40L at the same height as the aperature of the one on an installed carryhandle?

Thanks in advance,

Ted in Tallahassee

It mounts right to the receiver no riser needed.  The only sight that may not have the correct height is if you use a Colt barrel.