I haven't shot any .38 special in a long time. From memory, like 5.9 grains of 231 under a 125 grain JSP? I can't swear to that. It's probably in the +P range. I still have some left over from plinkin' loads for an SP101 .357 I had 15 years ago.
In .357, 13.5 grains of 296 under a 180 grain Nosler HG partition. Fresh-trimmed WW brass, Fed 200 primers. Half inch at 50 yards from my scoped 10" contender.
17.5 (!!!) grains of 296 under a 158 grain XTP HP, same primer and brass. This is WAY over max but was a "book" load when I was working up loads for my GP100 and Blackhawk years back. Shoots good, but when it's used up I won't load any more, I don't want to risk getting it in my J frame S&W.
I used to run 16.0 grains of 296 under the Sierra 170 JHC. Same situation as with the 158. Sierra reduced that quite a bit in later manuals.
A marlin lever action I had for a while liked about 20 grains of IMR 4227 under a 125 grain XTP HP. Mostly though I used around 13.5 grains of AA#7 under that bullet. Both of those were with WW small pistol standard primers.
Don't rely on my .357 loads. Lot of that stuff was worked up for heavy framed guns years ago. We decided blue pills were not hot enough so we created the purple pill. ('cept shooting those tended to create shrinkage, not ... "extension".
Fear of death will have that effect.) We created something else we called a +T load, "beyond Taffin", after gun writer John Taffin who had some pretty, um, energetic loads in data he wrote up in American Handgunner over the years. So, sort of joking around here but seriously if I had to do it all over again I'd not be pushing the poor little .357 quite so hard. Nor the guns. Nor the body parts nearby.
I never blew one up, but one time I saw a S&W 19 with a distorted frame, one chamber wall bent out and cracked. It changed my view of the whole "crowding the envelope" deal. What really got my attention was the 'tard was still shooting it, he'd just open the cylinder to turn it past the mangled chamber 'cause it was bent out far enough to block the gun from cycling. Shouldn't have been a surprise, the same guy showed up later with a 1911 clone in 10mm he was mad at because (being the gun's fault of course) the barrel had split inside the slide and tied up the action.
If you are loading for .357, pay attention to primers vs powder. Magnum pistol primers can have a huge pressure increase with 2400 with minimal velocity gain. It can sneak up and bite you in the a$$. If you get a sense of being slapped in the front of the pants leg by the shock waves, back off. Real hot 2400 loads feel like something is detonating, not burning. Some of the older data can get you into real trouble. I'm not joking about that at all.
Tom