All the big magnums look great on paper - to a certain type of person - but they are not used to win matches very often. Here's the data from the 2010 Steel Safari

http://demigodllc.com/articles/steel-safari-2010/?p=3
The 6.5mm caliber totally dominated with 39% of all rifles; 6mm was next with 28%, then .30 (22%), and then 7 mm (11%). Specific cartridges: .260 Remington (25%), .308 Winchester (17%), 6.5x47 Lapua (11%), 6% for each of 6XC, 7m WSM, 7mm RSAUM, .260AI, and then 3% each for .300 WM, 6mm-250, .30-06, 6.5-284, 6 Dasher, .243 Winchester, and 6CM/243
That's a pretty strong endorsement for the mid-size 6.5's. RayDog did win the 2009 match shooting his 7 WSM. We have had matches that allowed any cartridge less than .50 BMG-- one guy shot a .338LM and everyone else shot the normal cartridges such as those above.

I most often compete with my AW in .260Rem, second after that is split between my .308 (if I have cheap ammo to burn) or my AWSM in 7mm RM, which I will be shooting this weekend at the SRM.

-z