Thanks for the reply mag. Allowing 80 grains capacity for the WSM and 85 for the Dakota. Can the superior efficiency of the WSM case match the Dakota and overcome the 5 grain deficit? Seeking factual data. (30 Nosler=90 grains) I've never heard of a "WSM" action before. Let's go with "Standard Length" as this scenario does not limit the WSM to a short action shooting 200'ish grain pills.
In simple terms, no the WSM will not catch the Dakota or any other larger case regardless of action size.
A WSM action is the action built by Winchester to house there cartridge, it is smaller than a normal short action.
Even if you use a standard action, 3.4" mag length, the cartridge is still handicapped due to it's smaller capacity. The WSM just runs out of steam with bullets heavier than 200g.
There is an optimum weight for all cartridges where the bullet ends up taking up too much space to be propelled fast enough and you get slower and slower results as weight goes up.
The WSM is improved in this aspect on a standard action, as this is what I did back in '01/02 when I built 3 identical Win Model 70's in 25WSM (Pronghorn). But it can't beat the larger capacity rounds still.
Problem at the time was that no powder was slow enough except RE25, all other powder at the time showed erratic pressure and velocity.
Anyway, bigger cubes always wins.
Cheers.