How is accuracy with the 11.5 inch setup? Thats what I will have to do is SBR mine.sweet! What twist is yours? Wondering which it should be a 1/9 or 1/7 barrel shortned to 11.5" to get best overall accuracy figure it would make a big difference at that short? I would think 1/7 be best. My hbar post to be one but don't knoe for sure it shoots real good and its a older upper,maybe a colt but its a a1 upper reciever want to switch it to a3 FT. The hbar is 16". Wondering to cut it down or find another 1/7 barrel to cut down. I like 14.5" m4 myself with perminant brake that I had but heck might as well have a 14.5"one and also a 11.5",take this 16" and cut it down to 11.5". Whats best way to determine rifling twist since its not marked no where on barrel. I know you can use a rod but not sure what to use to make it stay in rifling to count twist.