I don’t know what it is, but the 58’s just handle nicely.
Not terribly accurate firing a .357 (.38 special) bullet in a .375 (.36 cal) barrel.
But its non-corrosive and a lot easier to clean. (And those converter cylinders make for a quick reload)
The ‘58s are my favorite. I had a gunsmith do action jobs on both and they are as smooth as silk, very accurate too. Had the barrel on the .36 relined to .357. I shoot black powder cartridges (which I reload) through mine.