Weeeelllll, the mere fact that you answered the question tells me that you don't reload. You ain't gonna find the 6.5 on any shelves, so that is a huge strike against it.
The .284 case is on par, case sized (more or less), w/the -06 case, that means that the .284 gives comparable velocity to the .280, and the 6.5x284 would match up w/a 6.5-06....fps and kick (and also 25-06 and .270). That gives is a few 100 fps (if that) advantage on the 7mm-08 and .260...whoop-de-do!!!
The fact that it is a reloading only type cartrdige kills it, in my choice. Don't get me wrong, tis a darn fine cartridge, but why???
In fact, IMHO, it has no advantages, over anything that you'd find on the shelf as the .260, .270, 7-08, and .280 all fill your bill and don't kick like a mule (they are have plenty of fps, accuracy and a short action, in my book, is not an advantage...or disadvantage). They've all been proven to be plenty of medicine for elk, brown bear, deer, antelope and yotes. You name it, they can do it (except for Griz).
The .260 is a wonderful, un-appreciated cartridge. Therefore, rifle choices are somewhat limited...unless custom. It has a long bullet w/a good BC and it really holds its fps, and it just may be the most accurate cartridge made. Maybe not, but it is more than accurate enough for 400 yards. You'll find it on shelves...low kick, accurate and it starts at 129 grains (I think) and goes up to cover your 140 grain target area.
Now, to cut to the chase, we are really at pretty much opinion (based on going back 2 paragraphs). But, I like the .270, .260, and .280, in that order,(bigger medicine, w/the same kick as a 7-08 and the only 7-08 I ever had, a BLR, kicked way more than my .270, w/reduced loads (in the BLR)). I'm a .270 man, and I like it better than 7-08...especially after I owned one that kicked (same fps for the same weigh bullet).
But, if you are limiting it to those two originally mentioned cartidges 7mm-08 is definitly the way to go.
John 14:6
