was wondering if any of the new muzzloader bullets are .452 diameter and load them in a 45 colt blackhawk, getting tired of hard cast bullets looking for something new..............

I thought the opposite was true ...452" pistol bullets loaded into 54 calibre sabots were the rage for smokepoles. As for the .45 Colt, you need look no further than Hornady's 250 grain XTP and a stout dose of 2400.

I like the TC 250 gr yellow tipped in my 45. It's out of a Contender carbine, but it's still a 45 Colt. Accurate, too. I didn't take a deer with them this year, so I'm not sure how expansion would be. Unfortunately, they're not sold per 50 yet and when you extrapolate the price, they're very expensive. More than the Partitions. But they still look cool
The Hornady ones are also .452 (they make the TC's, too)

I like the Hornady HP/XTP bullets no leading and both the 250 and 300 grain shoot really well in my Vaquero Old Model and my 45 colt rifle.

Yeah, the muzzle loader stuff is sold in funny quantities. I had picked up some swaged stuff that was 375 grain conical boatail that I paper patched for my 45-70. Came in boxes of 36, which was the most i have ever seen for sabot bullets. I am looking for something in .50 to use the sabots for, maybe a handi-rifle barrel in .50 S&W....