Rocketeer77 your fired cases being .297" at the end is good news and hopefully
@BrentM will measure his fired cases to let you know what they measure at the base of the neck.
As BrentM mentioned the SAAMI chamber drawing does have .001" taper so your cases should at least show that variation.
Can you please tell us what primers you are using?
Why I ask is because I read a comment by Steve from Hammer Bullets that they have found that the 6.5 PRC shows higher pressure when they used Magnum Primers rather than Standard Large Rifle primers.