No one in the benchrest community has answered your post, mostly, I think, because AFAIK, there is no 600 yard benchrest near you, and because your rifle won't be competitive in a benchrest match. There is no "factory class" per se offered by any of the sanctioning bodies. Whether or not a club chooses to offer a factory class is their concern.
But it sounds to me that NRA's (Highpower) F-class might suit you better. There are likely a number of clubs that shoot 600 yard F-class (highpower). There is one in North Carolina that shoots at Camp Butner, which is off exit 191 on I-85. (We shoot 1,000 yard benchrest there, too).
Perhaps if you give us a bit more information, like benchrest or F-class, approximately where you live & how far you're willing to travel, we could be more helpful.