I don't know...I keep scratching my pointy longeared head over this one. At what point do you get over-case capacity for the bore and just start blowing powder out the end because of the physics of the size of the piston the combustion/pressure front is pushing is too small to be efficient?
(EDITED at this point to get back on track to the original question...sorry)
I suppose if you have a need for .300 WM performance in a rapid-fire situation, then I'd look long and hard at the .300 WSM in an AR10. As far as any bolt action, then if you need a short action mountain rifle or carbine like a Browning Micro or a Remington Model 7, then you get to punish your deltoids to your hearts' content. Sorbothane recoil pads are much less expensive than rotator cuff surgery. Marketing people exist only to make you buy something that's 'new'. You have to decide for yourself if it's really 'better'.
(end of tracks; now I'm back to the derailment)
I mean, it all sounds great, but really, how fast can you fully combust a powder charge of roughly 58 grains in an overbore cartrige against a .224 diameter piston yet expect NOT to see flame cutting of the throat and leades (see 'Ruger Blackhawk', Dan Wesson' and '.357 Maximum'). One of the most anecdotally reported problems with the .220 Swift and the .264 Winchester Magnum were barrel erosion and reduced barrel life.
Spiffy, fast burning powders are great if you have enough surface to act against in the amount of time the 'piston' (bullet) is in the barrel, but I think, for my money, it's so much hot air for the cost vs. lifespan of the firearm. I think the mini-magnums are going to end up being a footnote, especially if the companies persist in loading them up to maximum velocities. In throttled-back loadings, they very well could end up being significant new target loads, but as far as thunderbolt-hammer-of-the-gods-reach-out-and-smite-them ultimate hunting loads, I'm not a believer yet.
Besides, in Texas, the minimum caliber for deer hunting is .23 caliber. Can't use the .223 WSSM for deer here, anyway. Winchester states that the ".223 WSSM 64 gr. Super-X Power-Point is for antelope, deer, and black bear".
Sorry, not in my back yard.
http://www.shortmags.org/shortmags/ref_data/ballistics_223.pdf
Regards,
Rabbit.
...who likes 30-06, 6.5x55 and regular .223 just fine, thanks.