BudsGunShop.com - Break in.

Harold, CheyTac does not have owners manual on line, so I would contact them direct about a break in procedure (although I'm sure it's about the same as any other AR15) 731-535-6029 or email sales@cheytac.com
In general, you will lose about 200 fps with an 18" barrel compared to a 24" with 6.5 Creedmoor ammo.
Stay safe & have a great day!

most modern firearms do not require a break in period for function

Hi Harold and welcome. Break in is a series of 10 or so 5rd groups with a bore cleaning between each group. This will properly season your barrel. Next I would try a variety of ammunition to see which your rifle likes best accuracy wise. Once this is determined, get a nice supply of the most accurate ammunition. Thers will be marginal velocity loss with the shorter barrel but not as much as one would think due to the relatively quick burning powder used in most 6.5 Creedmoor loads. Cheers and stay safe!