Simply which would you choose and why? What are the differences in the barrels in the two. Im not sure which one is thicker, is the Car from Rock River thicker or the Bushy, and what is the diameter of each... My dad and other friends have Bushmasters, and have never had a problem. Can i expect the same from Rock River? And is the hand guard on those Rock Rivers longer then the Bushmaster carbine hand guards? Is the only difference in the bushmaster M4 and the 16" carbine the barrel? Thanks for any input.