Wow, I had seen people comment about a "stinger" or say their hand was sore the next day after shooting 357 Magnum from a small revolver. But my right hand near the base of the thumb is sore and so far not improving. Wondering if I just seriously irritated the joint, or if I could have a minor fracture.
Story behind this is I got interested in the Kimber K6s, and settled on a 2" with the enclosed hammer and stock rubber grip. This was to use as an alternative to my typical compact 15-rd 9mm type of semi-auto, possibly more comfortable to carry. At the range I tried .38 special first, no prob in the K6s. So I had some old 357 Mag RWS range ammo, FMJ round-nose 158 grain. Got through about 30 rounds I think. The first couple cylinders hurt, but of course I told myself to "man up" and shoot more. This was a week and a half ago, in certain directions of stress the base of my thumb is still really complaining.
So, I am 6'4", 210lbs and have really big hands, to the point where most XL gloves are too small. I shot a bunch of 357 Magnum out of my GP100 just a few weeks back, no issue. I have never had hand-pain after shooting in my life, and I have shot some big rounds like .45 Super out of an HK USP and never noticed anything afterwards. It seems like a combination of that short grip on the K6s and the completely exposed backstrap did a number on the base of my thumb. I have the "Control Core" grip ordered and on the way from Kimber but they are slow to ship. Probably a good thing, and also good that the range I belong to was closed for de-leading this week or I would have been abusing my hand with some other pistol. Big Dummy.