The .30 T/C is basically the .300 Savage, and yes, apparently Hornady claims that's what they based it on. The .308 is slightly longer, and would work as well. But the 6.5 Creedmoor also almost identical to an older wildcat, the 6.5/.250 Savage RCBS Improved.
It would be relatively simple to make 6.5 Creedmoor brass from .308s, but dunno why anybody would bother, since even during this "shortage," 6.5 CM brass appears all the time on the Campfire Classifieds--and is far more easily formed from .22-250 brass, which is still relatively abundant. Unless, of course, your friend already has a bunch of .308 brass.