RE: bullet seating depth?
One doesn't buy 6.5-284 Benchrest guns from Gart Brothers - a gunsmith somewhere built this gun. I would get in touch with that person and find out if he set the throat to work with a certain bullet - or, as Jeff suggests, if he used a tight spec throating reamer. You may indeed have to put a little more throat in the rifle - but once you do this, there is no going back - without setting the whole barrel back and starting over with the chambering process. I would explore what you have and what it will/won't do first.