IMR4350 will be your best powder choice. H4350 may be even better for longer barrel life as it burns just a tad cooler.
With the case volumn of the .264, reduced charges are not recommended. However, Accurate Arms lists some reduced power loads for XMP5744.
Also, H4895 can be used but loads aren't all that much slower than IMR4350.
Lee#2 has H4895 data showing a start load of 50.5 for 3350fps and 55.0 max at 3,625fps.
I'd suggest you start at 50.5 and work up to best accuracy. This will "save" your barrel.
I have a .257wby (closest 'cousin to the .264). With 85gr bullets it's a laser beam to 400yds... However, with the light bullets and heavy charges of slow burning powder, it can be a "barrel burner".....
Don't do what a friend did with his .22-250 and 40gr Nosler B.T.'s. He burned out his barrel in a single afternoon on a prarie dog town....
Shoot 3 times and wait 5min, minimum and clean every 20rds or so.... This will keep down copper fouling and keep your barrel cool...
