I started my centerfire rifle career with two 1959 Model 70 s in 264 Win Mag with 26 inch barrels. I never have purchased factory ammunition for a rifle. I shot a lot of 1 and 3/4 inch at 100 yard groups with those rifles. My next rifle was a 7mm Rem Mag Super Grade (Mauser longspring extractor) with at 24 inch barrel. It shot about the same as the factory 26 inch hammer forged tubes in the Pre 64s. I discussed the problem with Ed Shilen, the button barrel maker. He said the best bullets of the time were not capable o more than an inch and a half regardless. He said that Sierra's standard for the time reflected this. Compounding this was the selection suitable slow burning powders ended at Hodgdon 4831. (Yes, there was surplus 870 but I never got that powder to produce more than 2900 something in spite of the published data. I even used duplex loads with 3 grains of Red Dot over the primer.) When Reloader 22 became available, my groups got a little better.
My arguement against the .264 Win Mag is that in the Model 70 (I still proudly own 6 of these rifles), is that the cartridge was designed for flat based spitzers and these were deep seated into the body of the case to fit the magazine length of 3.4 inches. The modern 6.5 WSM, SAUM or Hodgdon cases will fit the same magazine and take advantage to the Berger and Nosler boat tailed VLD bullets seated to the shoulder for better accuracy. The cases, without the belt, are much more consistent in thickness and do not separate just above the belt. I still am loading a M70 factory barreled in 7mm Rem mag. I seat the bullets to the lands and the rifle functions as a single shot. Neck turning will show just how out of round the Norma (Nosler the same) or other belted cases are.
A custom .264 Model 70, built on the extended length 375 or 300 H&H length action would be better for accuracy and handloading. The other option I would recommend, would be to put a quality custom barrel on your Super Grade rifle in 6.5 SAUM (great brass cases from Atlas, Peterson, etc) or 6.5 WSM (poor brass from Winchester or Norma) and get it set up for the long range Accubond or Berger bullets.
The good news for handloading is that the standards for bullet accuracy in 6.5 have improved to those for 30 caliber. The other thing that 6.5 magnums have in favor is the powders (especially Reloader 26) can deliver velocities and consistency that we dreamed of for decades before. And shorter 24 inch barrels will get you to 3300 fps, 140 gr bullets with Reloader 26.
Always shoot nitrided barrels with coated bullets to double your barrel life.
