I have a Cooper M21 Custom Classic in 223 Rem. I bought it in 2008, but it could have been made earlier. The point is that it has a twist rate of 1:14. Until recently, most factory 223's had a 1:14 twist. Now almost all, including the Coopers, have a twist of 1:12.
Here is twist info from an article on the 6mmbr.com web site regarding the 223 Remington. It lists the maximum bullet weight versus twist rate:
1:14 - 55 gr, 1:12 - 65 gr, 1:9 - 73 gr, 1:8 - 80 gr, 1:7 - 90 gr
For more info, here is the URL for the 223 Remington: