The M4 won't co-witness... GSR sights are too low. You could maybe fabricate a mount for the Burris Speed Bead... but that would end up being behind the rear sight.
You might be able to fit an offset mount, so you can use the irons straight up, and the M4 at a cant. Or a flip-off mount... but that might block the irons.
All I got...
Shoulder Drive Nicholson Club