I'd say go for it. The standard 1 in 10" twist stabilizes 105g Speer Spitzers out of a 243 just fine, but the VLDs are longer so a somewhat faster twist makes sense. Have you considered a1 in 9" twist and run the numbers? When I had a 243, I loved shooting those sweet little Sierra 70g HPBT varmint bullets at 3400 fps. Those and the Speer 105g spitzer were my goto bullets for my 243.
My 270 Weatherby brass is made by Norma and is excellent. I fireform my 375 Weatherby brass using Remington 375 H&H brass with reloads which also works well.
