Last night the Coyotes were back. Been almost 2 years since I had to kill one and they left. Using an older Bushmaster AR with the 1:9 h-bar barrel chambered in 5.56. I've been using some 50gr AE .223 tipped varmint. range is about 25-40 yards, reddot is sighted to 40 just for this purpose. Is this the right ammo or should I be using the 55gr 5.56 or?