So I’ve been trying to zero in my Eotech EXPS3-4 with G-33 3x magnifier on my Bushmaster XM-15, just when I think I’ve got it dead to rights at 50yds it starts shooting 2-3 inches left or right with no intervention whatsoever, completely repeatable too. I mean it’s still deadly accurate, I’m going to hit what I’m aiming at no problem but I wanted to get my grouping basically on top of each other. I thought it was maybe I’m just a crap shot or my optic is defective, but a buddy of mine said that it may have to do with the carbine length barrel and the fact that this rifle just isn’t designed for that kind of accuracy. Does anyone have any insight to the issue I’m having?