LS,
I have a Swansleeve on my 458, with the flip up rears (a 38, I think), and a Comp ML2. The front is the DPMS 3 rail gas block, with a BM flip sight. When I picked up my ML2, I also picked up a spacer. Did not need it. When I mounted the ML2, it was only 5 or 6 clicks down, and a couple to the left of being perfect. I can look over the flipped up irons to see the dot, or I can flip them down for a better field of view. I have a pretty good cheek weld.
Man oh man, what a cartridge. With my sitting bipod, and my ML2, I can hit targets, see the impacts, and get onto the next target pretty darn fast, without a comp. As a matter of fact, I have this certain metal spinning target that needs mending, as I Hammered it to death with 4 fast shots at 80 yards. It broke the welds. A semi-auto 45-70? Now this is horsepower......
Craig