I have been considering this very issue myself. The next one will defintely have a 26 inch Carbon wrapped APS barrel. Currently my Edge has a 30 inch Lawton Fluted Sendero profile which isnt the lightest!
I have also shot a 300 win mag C/Arms in their middle spec model and it shot very well despite the critics even with factory ammo. I feel the Carbon one extreme would perform very well. I have no doubt it would shoot 1/2 MOA and I am in another country so we always pay more despite current dollar parity. I'm use to it!
C/Arms have launched into Australia now.
No doubt a carbon wrapped 26 inch barrel is the go and if I had my time again I'd pay the extra for the APS with possibly a Rock Creek barrel . Nothing wrong with a stock 338 RUM in a 26inch barrel. I suppose you could always fire 250's for a bit of reduced recoil.
A buddy is currently chambering a 7mm RM to 338 RUM with a 26 inch pacnor No4 so that will be interesting to see how that goes in comparison. He will be fitting a DE brake.
I have also owned and shot a few Weatherby Accumarks in 30/378 and 338/378.
Dont let anyone tell you they cant perform well with carefully worked up handloads.
I virtually put 3 in the one hole with the 30/378 at 100 yards with 210 Bergers.
The only mods are Timney trigger and a decent bedding job to the B&C stock. Seat the bullet to mag length and with the right load above what the books say they shoot!
The 338/378 brake needs to be better and we did get at tad better recoil reductions with the V port vaporiser. However we feel we ned a better brake again . It will deliver 1/2 MOA with 300gn SMKs in a 9lb bare rifle. On my Edge I have had the new mini extreme fitted but I havent fired it yet with this brake.
You are lucky you have such a big choice and numerous smiths in the US.