rtoney, you need to provide a bit more information about your planned uses. When you are suggesting target shooting, are you referring to: bullseye or steel? What are you considering hunting? At what distance are you looking to shoot?
When I was physically able to shoot NRA "across the course" matches , I used a 1:7 Colt HBAR and shot out to 600 yards. The general rule of thumb at that time was a 1:9 barrel was good to about 300 yards with up to a 72gr bullet. With bullets up to 80gr, a 1:8 or 1:7 twist was preferred, and would reach accurately to 600 yards.
Personally, I wouldn't want to stretch a 55gr bullet much beyond 300 yards. This is just me, but for hunting, I wouldn't consider using a 223 on any critter larger than a varmint (such as: groundhogs, prairie dogs, fox, or coyote).
I was weened on bullseye, so I can't really speak to the 223s capabilities on steel or mention a maximum distance for a 55gr bullet.