Try comparing 158gr loads - like a Remington R38S12 158gr LHPSWC +P .38 Special. It'll make from 850+ fps from my 2" 10 to 995 fps from my 6" 66, still subsonic and less the earsplitting 'crack'. Now, try the 158gr JHP in .357 Magnum - probably 1220-1260 fps, depending on other's testing, from a 6" barrel (I've never fired real .357 Magnums from any of my .357 Magnum revolvers.). Definitely supersonic - and loud - and produces 60% more kinetic energy than the +P, which is 40+% more energetic than the basic .38 Special, making the 158gr .357 Magnum over 2.25X the regular .38, KE-wise.
To insure proper 'ignition', a better primer is needed - actually, one that produces a hotter & longer flame - a small pistol Magnum primer. Some primer makers have a 'one size does all', however. The longer case further insures the round will only be used in a properly designed/rated revolver. It's predecessor, the .38-200, didn't have that feature, much to the chagrin of some fine .38 Special revolvers of the day. The .357 Magnum was in answer to J. Edgar Hoover's request for a car door piercing round, so G-men could effectively retuen fire at fleeing felons of the day (Twenties to early thirties.). Doug Wesson took the first unit around the country - and took unbelieveable game with it. Great proof. Of course, today's cars could likely be holed with an AirSoft gun!
I bought .357 Magnum revolvers, and even a .38 Special is still .357" bore - semantics, for one reason - availability. There are few six shooter .38s - and no 7 or 8 shooters, much less any barrel length selection. Of course, I reload many a .357M case - with .38-ish level loads. Hey, I like wimpy - the plate still makes a 'ping' and it still makes a hole in paper targets. That's me - YMMV.
Stainz
