In my own experience it would be hard to beat the 223AI or 20-223AI (AKA 20 Sploder). Those aren't far behind the BR in accuracy or velocity, and brass is so much easier.
When I go PD shooting I start with one of my 22 Spitfires w/40 gr bullet, then move to the 20-221AI w/32gr bullet, then to 20-223AI w/40gr bullet and if conditions/distance warrant it I will finish with one of my 6mm rifles. Everybody has their own game plan, this is just mine and has worked very well. Where I go I usually shoot 300-500 rounds/day so starting with the small stuff helps get a lot more shooting in before barrel heating becomes an issue.
When I go PD shooting I start with one of my 22 Spitfires w/40 gr bullet, then move to the 20-221AI w/32gr bullet, then to 20-223AI w/40gr bullet and if conditions/distance warrant it I will finish with one of my 6mm rifles. Everybody has their own game plan, this is just mine and has worked very well. Where I go I usually shoot 300-500 rounds/day so starting with the small stuff helps get a lot more shooting in before barrel heating becomes an issue.