If you go with the 6BR pay attention to barrel twist. You need a 9" twist to use the heaver bullets. With a 15" barrel you can get 2800 fps with 85 gr bullets, 2700 fps with 90 gr and 2600 with 100 gr.
I picked up a Contender barrel 14" in 6mm-225 Winchester plus loading dies in an estate sale CHEEP since it was a wildcat caliber. It about duplicates the 6BR. I get 2850 fps with 30 grs Varget with the Sierra 80 gr SSP bullet. My problem is that the barrel is a 12" twist and it will not stabilize any thing heaver than the 80 gr bullet. I shot around 10 deer with this combo but decided that it was too soft a bullet for my liking. On broad side shots inside 120 yards, longest shot I made, it would not exit and deer would run off some and did not leave much of a blood trail. The last 4 or 5 I used neck shots. I would weight until they were facing me and when they put their head down I would shoot them where the neck meets the body between the shoulders. It dropped them in their tracks from cutting the spine. I did get some 85 gr Nosler partitions to see if they would shoot but never did get around to trying them. I got a 14" MGM made 30-30AI barrel that became my deer barrel. It is AWESOME with 125 ballistic tips at 2670 fps and it SMOKES deer. I just use the 6mm-225 for varmints which it does a great job.
Don't know about the 6.5 Creedmoor in a pistol barrel. But many of the 6.5 bullets 120 to 140 grs are meant to use in the 2400 to 2700 fps muzzle velocity range and that should be doable with it. They would be better for the 200+ yard shots for deer.