Well, for a gun that has been in the use of the Marines for many years before such smaller optics like the MRO and XPS2 or XPS3 they used a lot of the EoTech 512's. My first M4 had a 512 with several thousand rounds with no problem. The Vortex is only 2 oz more in weight. The way I see it, if it can't handle it, I DON'T NEED IT.