6.5's work well for a tactical rifle. But, anything above a .308 sized case gets to be overbore. If you've read much you know that guys shooting the 6.5-284 go through barrels when loading hot in about 1000 rounds. That's why most everyone shooting them has reduced case size to .260, 6.5CM 6.5x47... One that remains popular, especially in Europe, is the 6.5x55. It's not loaded to as high of pressures as the previously mentioned cases, but it has more case volume. Loading more of a slow powder to get that longer push and you have about equal ballistics. You can also improve the 6.5x55 and that gets a lot done without going so big as the 6.5-284. It still shortens barrel life though. Bringing me back to the single point of no matter what cartridge you choose, picking one that goes above 2900 in the 6.5 bore is going to eat barrels.
That said, I chose the 7mm-08 specifically for that reason. The 7mmCM is coming along as well. A little different shape to help it handle going through the -10 platform better. Or, I should say with full length total BC possible bullets. Given case lengths, you can load a 180 Berger VLD in a 7mm CM and run it through that platform. You can't with a 7mm-08. You also have problems running that combo through a Remington 700 Short action. But, unless you really need to have a shorter case, it doesn't matter if you go with the CM or standard case. Another thing to consider is improving either a .260 Rem or 7mm-08. That gives a little more case capacity, but still retains the better case shape of the .308 over older styles (Mauser). In essence, you can load hotter because the straighter walls grip the chamber better, spreading out the force of ignition. Unlike a tapered case like the Savage .250, .22-250 Rem, and Mauser cases where the bolt thrust is mostly handled by the face of the case (head). That's why the 6.5x55 can't be loaded as hot as the current crop of 6.5's that are winning a lot in competitions.
FWIW, not all competitions have a velocity limit. And when they do, it's not always 3100 fps. I've seen it higher and even seen it as low as 2800. It's the shoots' sponsors that decide that. I'm not a big time competitor but speed limits have kind of always been in place so that the .308 can compete still. That's why when F-class got started, they had to make an F/TR. Palma uses only .308. On one hand it's good as it makes everyone shoot one standard. On the other hand that standard needs to be somewhere near the top capability. Making wind calls is one thing. Hoping the wind doesn't change while the bullet is in flight is another.
