Houston Boy
Not sure what has been rebutted yet as Brent points out that the 300 wsm has not been around long enough yet to say which is more accurate. However, think you will find that there will not be a spit of difference, depending on the day and the guy behind the gun.
Boyd and I are both using the 300 WSM in comp and doing fairly well. I also have an accurate 300 wsm coyote used for hunting and a factory class competition, so I have a fair amount of experience with the cartridge. I was one of the first to build a 300 wsm comp gun in the east anyway and won HG overall last year and group in state this year, but I can tell you it is not the cartridge that allowed that.
In theory the 300 WSM has an advantage with the shorter fatter (PPC style case) but after sorting hundreds of wsm cases, that advantage is countered by the poorer quality of the Winchester WSM cases and they require more sorting. Winchester cases have wide range of weights, case head size and thicknesses. Better quality win mag brass are available right now, but that might change in future as Winchester is tightening up on the wsm cases.
Fact is right now it is easier to take a 300 win mag, set it up and get it to shoot competively. The 300 WSM requires a lot more work. That is not just from me, but other top shooters that also shoot both calibers.
Also the 300 wsm tops out accuracy wise with the 210 bullet and many find the 190 is best while the 300 win mag seems to like the 210 and maybe 220s. Slight advantage to win mag here with the higher BC bullets.
Like I said, I like the 300 WSM as a hunting round in a short action but it has not been proven to be more accurate in similar guns at least yet and I doubt it will.
BH