I'm a big 264 fan I've owned 3 of them and I owned a sendero sf2 in 264 win mag. Still have the stock and action. It now wears a Brux 1-8 twist. The problem with factory Remingtons, Winchester's and Rugers chambered in 264 is they're all 1-9 twist. Mine shot ok but I wanted more. So I sent it to Score high Gunsmithing and had them blueprint the action and put the Brux on it. It shoots 140 Berger's-143 ELDX's between 3270-3300fps and is very accurate. Not much of anything I throw at it shoots over .5-.75 moa. Most are sub .5 moa. Barrel has around 700 rounds through it and is still going strong. I've had two of my buddies try to buy it off of me multiple times.
This is absolutely correct. The 9 twist in factory rifles is a definite disadvantage. The question is: How much of a disadvantage? The answer depends largely on intended use for the rifle.
The latest and greatest bullets are certainly out of the question, but some very good bullets are still in play. The factory 9 twist will stabilize bullets up to the Hornady 140 AMAX/ELD's, Sierra 142 MatchKing, and Berger 140 HVLD in most conditions (freezing conditions at sea level may require bullets with a shorter overall length). At higher altitudes in the mountain west, even the Berger 144 Hybrid will work. In a 26" barrel, the accuracy node for these bullets appears around 3150 fps, using Retumbo.
These bullets make the .264 Win Mag ideal for Mule Deer, Pronghorn, and Coyote in open country. If the intent is to use it for heavier game (such as Elk), or in tighter terrain, go with 140 Nosler Partitions. Though less ballistically efficient and decidedly less sexy, they will give you the terminal performance you need in situations where the bullet is more stressed at impact.
Because the .264 Win Mag is easy and fun to shoot, it begs to be shot a lot. Failure to resist temptation will lead to a replacement barrel, at which time the shooter will definitely want to upgrade to a faster twist.
It is true that a .264 Win Mag custom build, with a 7.5 or 8 twist will give the shooter access to the best bullets available. It is also true that the factory 9 twist is a handicap, but the handicap is not huge.