Gun was built by John Myer, Custom Gunsmithing in Boyce Va. He is one of the best in building 1000 yard guns and has built many top guns. He competes and knows what it takes to make a great gun. He is now making me a 6mm BR improved (shoulder moved forward .200). 28" Spencer HV taper barrel with 1-8 twist, 721 action, Bruce Baer laminated stock and jewell 2 oz trigger.
Clay Spencer builds top guns also and I think some of the absolute best barrels. Everyone says they are all "shooters", and clean up easier than anything else. The Army SOF just dropped a bundle with him to expand his barrel making business to build sniper barrels and SR25 barrels for Delta. They tested every barrel made in the world and his checked out best. They have combat SR25s shooting .5 with his barrels.
Have not tried the 210 JLKs. No reason, but after talking with Danny Brooks, IBS 1000 yd 1999-2000 champ, about his wifes gun, thought 190s would be logical. Lee Brooks has 300 WSM and she shoots Berger 210s at around 2950 fps with 30 " barrel.
Concensus on 300 WSM in 1000 yard shooters is that the 190-210s work best and most are going now to 1-11 twist instead of 1-10.