LRH with AR-15

[sscoyote]

I've got a Lee Mosher upper in .223 AI 1:9 I've been using the 69 gr. Nosler Match bullet on coyotes. I've had pretty good results with it @ right around 450 or so. Anybody tried to go any farther? I'm not sure if I'll get the needed energy/impact velocity beyond this range. Any ideas??