For instance, the .270 was recommended by some people. I've got one. It was my Dad's rifle. I can get acceptable accuracy for deer hunting with it but never anything really great. But maybe it is the cartridge? Have you ever seen a long range competition rifle in .270 Win? Or a sniper rifle in .270 Win? Maybe there just aren't the same level of bullets made for the caliber. Or maybe it is something about the cartridge design.
I have to admit I feel pretty much the same about 25-06 and .264 WM. They have the velocity but I just don't see super accuracy out of them. I'm sure somebody somewhere has one to "prove me wrong" but we're talking averages here. The average 25-06 just doesn't seem to be a half MOA rifle!
Long range competition rifles usually run in service calibers, magnums, or wildcats. The 270 is neither of these.
Sniper rifles are once again usually in service calibers, the notable exception is the 7mm Rem Mag (Secret Service) and 300 Win Mag (m24 variant).
But for a second let's look at what makes an accurate rifle, either for competition or tactical use. Start off with a heavy free floated barrel with a recessed target crown, add in a stiff synthetic stock with pillar beds and weight added to the buttstock, and eventually you end up with a rifle that weighs in excess of 10lbs and most over 15lbs. That is your "average" long range or "sniper" rifle. Match grade ammo (boat tail hollow point) is available but illegal for hunting in most states.
Your average 270 has a sporter weight barrel with a rounded crown that is in a hunting style stock, and if you are lucky it isn't an injected molded plastic. It weighs between 6.5 and 8 lbs. Match grade ammo isn't available because the 270 isn't a service rifle round or standard sniping round. But what is available is a large range of commercial ammo and reloading components that will provide a hunter with the opportunity to find the most accurate load for his rifle. Dave Petzal has a 270 that he just couldn't get to shoot any bullet accurately until he got some 140 grain 7mm bullets swaged down to 270 bore, and bam, sub moa (he says when he runs out of his current stash of bullets he'll retire the rifle).
Kleingunther, an old custom rifle company, guaranteed all their rifles to shoot sub moa with appropriate handloads. The one I read about from 1980 in 25-06 needed about five loadups before the magic load was found. Not a heavy barreled rifle either, just a long skinny sporter weight tube.
Now, if you decide to go the custom route and have a heavy match grade barrel put on an action there is nothing that is going to stop you getting sub moa accuracy from nearly ANY round out there.
Most hunting style 308's aren't particularly accurate with hunting loads, but they get the job done. The idea of "inherent accuracy" is valid, but the cartrige is only half of the equation. A lot of things have to work to get great accuracy.
Jimro
