The 260 has 2-3 grains more capacity and the 6.5x55 around five but I see loads for the Creedmoor that are faster than either. Is this due to the mythical cartridge efficiency or over optimistic reloading? According to JBs one quarter rule the 260 & 6.5x55 should get at least 30 to 60 fps more than the Creedmoor.
The Creedmoor doesn't run faster, guys here just seem to load it pretty hot.
As Bugger said, "pressure"... but, of course, the 6.5x55 data is pretty light on account of all the old rifles chambered for it.
“Perfection is Achieved Not When There Is Nothing More to Add, But When There Is Nothing Left to Take Away” Antoine de Saint-Exupery
