I know the saum and .284 fit in short action guns, you get barrels throated for the longer secant ogive bullets such as the 180 Berger and it works. You may or may not be able to use the magazine but that's not critical for F-class, for hunting I may use a different bullet if I can't use the magazine, or learn to reload quickly
I'm not sure what you consider a heavy low drag bullet for the .308, I shoot 178grain amaxs at a OAL of 2.965" and when I was shooting with .280fan last weekend he loaded his 180berger vlds to 3.1".
I am aware of the recoil, but I think with a limbsaver pad and either my can or a muzzle break in a 10-12lbs rifle it should be manageable.
I've heard good stuff about the 6BRX, good performace but not much recoil and inheritently very accurate.
I know the 6.5x284 is king, but at a very high price, the barrels burn out real fast, that's why I'm not even going to consider it, don't have the money to swap barrels every few months.
I do like the 260, seems like a good round, I will debate between a 6.5x47, 260, or a 6mm for my light carry gun on a later date.
I also have my ar15 which I am buying a bunch of uppers for to make it real versitile I think I have most hunting scenarios covered once i got these guns, the rest will be extras just for fun. I'm thinking a 6.5 or 6mm in a light carry gun, .284win f-class mid range medium game rifle, ar15 .300whisper with suppressor for deer and hogs within 200yards, ar15 .338 lapua or .416 Barrett for really long stuff/range fun.
I may get a 6.5x47 for my light carry rifle since it seems to be like the .260rem but a little more power, less case capacity= less powder so probably also a little better barrel life over the 260. I just liked the 260 because Kimber chambers the m84 in it, making it easier to get in a light weight package.