Hello GT, I just bought a S&W M&P15X. It comes with a standard M4 front sight post and a troy industries BUIS as the rear sight. I was wondering, do these rifles come zeroed out of the box or do you need to zero them. If so, how do I zero my rifle, and it if comes zeroed out of the box, how do I find out if my rifle IS zeroed. I am planning on getting an Eotec soon. How do I zero the eotec to the rifle. I am assuming you have to zero the rifle first, and then zero the optic to the rifle right? Also, at what range should I zero? My range only has 100 yards. I was shooting decently at 50 yards but then when I bought it closer to 25 yards, I did kinda bad. I did better at 50 Yards. Is this because the rifle is zeroed for longer range? Any help is greatly appreciated, Thanks.