An idea vindicated...
Sitting in boredom at work#1 (a thoroughly long story), I was surfing around and found out that Skeeter Skelton experimented with the .32 H&R Magnum when it first arrived, testing loads with a Ruger Single Six of presumably ~5" or so barrel length.
He claimed 100gr hard casts were pushed at 1600fps and 115gr at 1450fps. Now, 115gr pills moving at 1450fps.... isn't that .357 Sig territory?
That's probably bullet failure speed, frankly. But, it's nice to know it's been done before.