I'm a little behind on posting results, but I did get a chance to try some surplus 297 in the .450B two weeks ago. i shot a broad load work up behind the 250 grain FTXs, the top end of which is in the pics below. 2,200 fps will be in the 40 to 41 grain range at COAL of 2.250 It shoots just as well as 296, (those FTXs shoot pretty well loaded on top of just about anything). I tried it under the 325 grainers as well, but i was well under the "zone" on the first work up, down around 1,400 fps.
The 297 is about a grain and a half slower in the .450B than canister 296. It's also bulkier and coarser, but still flows through the measure just fine. The powder piles on the piece of paper are equal volumes, shaken slightly to see how they "flow". I'll try the 297 with 300 grain cast this weekend if I get a chance. I have about 16 lbs of this I got from Jeff Bartlett. He may still have it in stock.
BD