I got a new to me Rock River Arms A.R., I really like the rifle wich I will be using for predator hunting but it only shoots a little over a one inch group at 100. I guess that's not bad but I'm used to clover-leafing at that distance. It's the stock barrel but I really don't want the weight of a bull barrel. Is this normal? Also, I'm shooting .223 through it, would it be better to go with the 5.56? It's a 1/9 twist 16" with a 55 grain factory ammo...?