Inrut,
The .220 is doable, and I found out after I got mine back that the .243 extractor (If you have an extractor barrel) will also work. I finally had a chance to shoot mine this weekend. Mine is on the 24" Ultra barrel with 1:12 twist. I had 52gr hollow points cooking at 3800 fps, but the groups were not that great, still have to find the magic load for it. But yet, it works just fine.
Greg