Kaleb,
The 6.5 Creedmoor case is actually most similar to the .250 Savage RCBS Improved. The RCBS improved rounds used 28-degree shoulders instead of the 40-degree shoulders of Ackley Improved rounds, and 28 is very close to the 30-degree shoulder on the Creedmoor. It's close enough, in fact, for .22-250 brass to fire-from perfectly, with no trimming required, in a 6.5 Creedmoor chamber when using the Cream of Wheat method.
