I have had two 24" bull barrels rebored an rechambered by Ron Smith, both barrels shoot very well. Both used the the 223 H&R barrels. One was chambered in 6x47 the other in 257 Roberts.
Ron Smith is a well known Canadian barrel maker using cut rifling only. He has produced some world record holding Schützen Rifle Barels. Many of his barrels are in the US. Word gets around.