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Not sure about the actual velocity loss figures, although as I recall Doc Roberts has noted that the increase in noise, flash, and nasty recoil when using .357 in a J frame is not worth it. Gary's pretty sharp and objective; I'll take his word for it. When I was younger I might have tried it, but not now.
The Buffalo Bore load you mention would probably be far beyond outright rude. If you really feel compelled, get someone to video the testing and post it on youtube as a warning to all who ignore that prediction.
A solid wadcutter target load is actually reasonably effective as handgun rounds go, and actually shootable in a J frame. A moderate SWC as a reload would not be bad (WC are hard to reload with quickly). You are unlikely to get real expansion with adequate penetration using most HP loads in a snubby, but the square faced WC/SWC loads will cut well and give full caliber holes.
Remember that handgun rounds basically suck for stopping determined adversaries - and misses even more so! 4-5 hits with WC in the vitals will be a lot better than many other options. On those rare times I carry a .38 snubby, I use Black Hills target WC loads for all these reasons.