Creedmoor is a big bolt pattern, so you would need an AR10 for that. POF sells 6.5 cm AR10 called the Revolution that has the big bolt but slims down the gun to almost the size of an AR15 so its not as heavy and bulky. It even uses lots of parts from an AR15 so you can swap out parts universally, Thats the way I would go. Otherwise you can swap the barrel and get a 762x39 bolt/firing pin and convert your gun to 6.5 Grendel. It will work on a standard AR15 small bolt pattern. I used an old rig I wasn't shooting and converted in less than an hour. Grendel likes a longer barrel for powder burn but lots of guys are running 16" grendel barrels. I went 20" because I didnt plan on clearing houses with it.