Well, if you want to find one you pretty have to make it. No problem, just run a .44 mag case into a 357-44 die and you've got formed brass. As far as I know, the only factory gun you'll likely run into chambered for it is a TC Contender. It was, however, originally designed as a high velocity revolver cartridge. But it is mighty picky, as most bottleneck rounds in revolvers are, and isn't all that great an idea there. But where it really shines is in lightweight leverguns. A Marlin 1894 in 44 mag could be easily rebarreled and rechambered for 357-44, and you'd have pretty close to 35 rem ballistics in a light rifle that held a bunch of ammo.