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.
Agree....I don't think I have seen many claim the 6.5 CM is capable of velocities faster than the 260 or 6.5X55 when all are being loaded to a similar fashion. The latter to cartridges should always out run the 6.5 CM as like you said they have more room for more powder.
