.338 LM or the AI version. You will not beat the Lapua brass. It IS the cheapest you can buy and consistancy second to none. For an action go with a custom Defiance or find a Wby Mark V. I would go with a 1 in 10 twist Hart or Lilja. The 26" is OK but I would strongly condider 28" plus brake. Contour should be in the Rem Sendero at least, with a muzzle dia of .830" or so. Have the barrel maker flut it with 6 1/4" flutes before final stress and lapping. Brake... JP Precision. McMillan Lazeroni Thumbhole stock. NF 20 MOA rail, NF rings and a NXS 5.5~22X56 with a NP-R1 Reticle. Load her up with H-1000, CCI 250's and 300 gr Berger OTM's. Then prepare to be amazed.
Can you tell I have been thinking of one of these? When my 338 LM barrel wears out, My rifle will probably get a make over to this exact rifle. But approaching 1500 rounds soon my 338 LM is still a solid 1/2moa rifle to past 1400.