In all actuality they have. Downloaded 350 Legend would be about the same as 357 retuned to get subsonic loads. 450 BM subsonic ammo will be like 45 Colt, which is so close to a 44. When I saw this thread a few days ago I was really jazzed as I could think of the possibility of 44 mag subs. The more I chewed on it I realized that with my can, and having the American in these calibers already, I could do a lot of subsonic load development for way less money than a new threaded 44. I already have 2 77/44s in the safe. If I could get just the barrel I’d be in. Neat idea but that’s just stupid money for what I already have. The only real benefit I see is you’d be loading with carbide dies. Either way I don’t anticipate any ammo company making much subsonic 357 and 44 ammo so I’d be back to rolling my own anyway.