07-07-2012, 11:17 PM
assuming your doing a 308 ar10 yes a 12.5 inch barrel will kill your ballistics you will be looking at similar ballistics to a 7.62x39 you could put a 1in8 barrel on it and shoot 240 gr bullets to gain a little ke and ballistics but overall it is not going to be a particularly practical long range platform though the muzzle flash is going to be a formidable weapon

