Re: Cartridge design help please
Guess I'll throw my 2 pennies in... The Howa/Vanguard actions are a little on the short side compared to the 700 (I like the Howa's better) so, if you want to efficiently seat thse bullets to maximize case capacity that rules out cases like the 300 WM, 300 WBY, STW, etc.
The 257, 270 and 7mm WBY's have about 3 gr more powder capacity than the 270 WSM. Not a lot of gain in performance there, and IMO the WSM is a more desirable and efficient case.
I'm guessing here, but I think the hoped for velocity is possible with the WSM and Reloader 33. What you are asking for is an overbore case in which you want to shoot heavies out of, which means you need a slow burning powder like 33. Using a relatively short barrel less than 26" is going to cause a good loss of efficiency in that scenario. A 26" barrel including brake is going to be about 24 1/2" long.
My vote goes to the 7 LRM and there should be no problem reaching the desired velocity in that case. The down side is more expensive brass (but good brass), a new custom reamer and custom dies. I don't really consider custom dies to be a downside when it comes to precision shooting.
With the WSM, you might need a custom reamer for the 165 bullets but off the shelf dies are plentiful and Norma makes brass for the WSM. The downside to the WSM is you might fall a little short of the desired velocity (maybe not) but over all you will have less cost. A full 26" barrel would help.
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