Hi Tim
There is a discussion on an overseas shooting forum about it at the moment ( I started a bit of a disagreement it looks like- typical me

)
The 300WSM looks to be the one to beat at the moment.
However Shiraz Balolia has written up his experiences on shooting one:
"
Imagine two people standing over you. Every time you take a shot one guy whacks you on the head with a baseball bat (that's the .300 big bang effect). The second guy stomps on your shoulder with his rough soled, steel-toed boot (that's the kick). Other than that the .300 is easy to work with 
Seriously, though, with the .300 I think the match adrenaline keeps me going during the day, but when I get back to the hotel room I cannot even lift my arm up, and after that its Ibuprofen city. By contrast the .284 Shehane is very pleasant to work with and has very decent performance. A lot less recoil and deadly accurate."
Im personally not built for it I dont think- will be trying some big boomers soon to see but I reckon the 284S is going to be my limit.
The argument I started on another forum was basically one guy was dropping points with his 6 dasher so wanted to go to a 30 cal to get higher scores. When I recommended he learn to read wind that didnt go down well but I stand by it, miss a decent wind change and your going to lose points. Sure good BC and velocity will help minimise it and I understand that is the beauty of FO but you dont want to be losing points in the first place. Im sure every shooter in the world doesnt have equal wind reading ability (me included

) so I feel that should be an area to work on more so than trying to let the caliber do the work.
Interesting to see for those who are going to try out for it, the next FCWC in canada, those shooting 300WSM's may have to load down a little to get under the velocity/BC ratio for that range. Looks like 284S in high nodes and maybe 7RSAUM around 2950-3050 fps will be about the limit. Someone wanting to run 230gr hybrids in a 300WSM wont be allowed to do so.
In terms of the biggest, most ranges have a limit of 8mm so how big a case can you go? A shooter at my range has a 30-338LM but he doesnt shoot it much more than 12 shots a day due to the sheer recoil and muzzle blast factor. Some ranges are now starting to put in place velocity and muzzle energy limits too I think so you will probably want to check with your range first.