The caliber is a 6mm Creedmoor, not Rem. It comes with a 7.7 twist and will shoot the 108’s etc quite well. They will easily go past 1000 yards, probably the majority of 1000 BR shooters are using various 6mm like the Dasher, etc.
I bought two of the Ruger Americans, one in .243, the other in .30-06, gave them to my son and oldest grandson. Both will shoot in the .5 MOA range, I think I paid $349 for the new one.
I've owned two .243 Win caliber rifles. Ballistically speaking, their doesn't seem to be a dimes worth of difference between the 6mm Creedmore and the .243, other than the fact that 6mm Creedmore rifles have a bit faster rifling twist to stabilize the 108 gr bullet better. You made the wise choice with the .243 rifle. But, the ballistic coeffcient of the 6mm Ceedmore round isn't nearly as good as that of it's 6.5 bigger brother.