RE: .204 ruger or .223 rem. ???
The .204 is a fairly new round and is proving itself a challenger in the predator hunting world. It is faster and flatter than the .223. 400 yards would be stretching it to the limit, as would the .223! 300 yards, should be jsut fine with either cal. If you will have a high percentage of 400 yard shots, maybe you should concider the 22-250!
Ammo. suited for coyotes in the .204 is hard to come by right now, unless you reload. The .223 ammo. is some what cheaper too. the v-max bullets have been found to lack penetration on coyote side critters out of the .204. The most popular bullet choice so far is the 35 or 40 gr. berger bullets!