This will be my first AR, but I have sho them before. I have a mini-14 tatical for anything under 200 yrds. I like the AR platform for the accuracy it has, because I like long range shooting out to about 450-500 yrds. The bushmaster is $849 and the R-15 is $889. The bushmaster is a flat top with a carry handle and 30 round magazie. The R-15 is black, and comes with a 5 round magazie. Is the R-15 chambered for 5.56 or just .223 rem? Thanks for the help Sorry if this is in the wrong section.