1/7 twist is only better for ammo that costs more to shoot than 55gr. For range use, you'll be shooting 55gr fmj 99% of the time, so why spend the extra money on the upper and extra money on the ammo? If you're not building a combat rifle, there is no advantage of going to 1/7 twist. If you are building a precision target rifle, then stick with a .223 upper to maximize precision. Just my 2c's.