7ultra; great thread, lots of opinions. I don't know much about the small caliber Wbys (see my signature and previous post), but I've got to throw this in: The .338x.378 that I'm building has chronographed a very modest 2760 fps instrumental, on an Oehler 35P, with the 300gr Sierra mkhp. 5 rds, s/d 7. Using Oehler Ballistic Explorer, that load will deliver just over 2,000 ft# at 1000yds, and just under 1,000 ft# at 1 mile, and it's just a starting load. It put 5 rds in 3/4" at 100yds, will fit in the magazine well, and the rifle weighs 13 lbs. To me, that's a helluva start.
I don't know much about the "designer" cartridges, but I do know that for a caliber that has available factory brass, this one delivers the mail.
IMO, if a factory Wby MK V won't shoot good enough to suit you, it's a great action to build a custom on. You may have guessed---they're my favorite.
I told JECustom that his .30x.378 (5 shots in .091") might not win a benchrest match, but it would if he shot first!
Have fun, Tom
Texas State Rifle Association Life Member
NRA Endowment Life Member
A big fast bullet will beat a little fast bullet every time