Congratulations of your new rifle. I too own a Century Arms CETME. And I also live in Arizona. Don't worry, .308 "lethality" is considerable way beyond 400 yards. My CETME is surprisingly accurate, and to enhance that, I mounted a 3x-9x scope on it, and as successful as that was out to 200 yards, I am now considering upgrading to an all out 8x-32x or 10x-40x power scope. Why not? They can be had for under $150, with illuminated reticles and rings included. While my CETME is not as accurate as a dedicated bolt action target rifle, properly sighted in with such optics I could easilly guarantee a hit on a Democrat sized target at 600 yards or so. At shorter ranges, I am happy to rely on my .223 and 7.62x39 rifles.