You sure you’re not thinking of a 6.5 Grendel?Oh, and just to clarify...
The Creedmoor was designed to fit long, heavy match bullets in an AR type MAGAZINE without the bullet encroaching into the powder.
The ACTION length had nothing to do with it.
I did my research before posting. Even if it were designed for AR-10 magazines, it would still be short action length. Both lengths were based around the 308, which coincidentally has an OAL of 2.81”; a standard AR mag has an OAL of 2.815”.
In my research today after reading your comment, I did not find anything about it being for an AR at all, and in fact found in favor of bolt actions, which wasn’t mentioned a lot. It was designed for long range target shooting, which is typically done with a bolt gun.