Anyone suppressed a 17 hmr, did it make it quite enough to justify the trouble and cost? One more does the $200 dollar tax go to the Pittman-Roberson act?
I know you're looking at a second barrel for your 455 - but if you're contemplating reloading, consider the .22 Hornet and .17 Hornet, as well as the K-Hornet and AI variations.
People shoot undersized rounds through cans all the time. A .308 can suppresses a .223 fine, even if it's a bit louder than a .223 can, and I've seen 9mm cans marketed as a solution for .223 and 300BLK as well as .380 Magnum. Perhaps your local NFA shop can give you a personal demonstration?