Depends?
?
On bullet fit/size, barrel size and quality, size of cylinder throat, pressure, velocity, etc., in short you can work with generalities but like .22s each gun is a situation unto itself.
My son and I were both shooting Black Hawks and while I could shoot non-gas check bullets for extended periods with little or no problem, they leaded his gun. We are talking Mag. loads.
We went to gas check bullet design with the seated gas checks for his gun and no more problem.
I shoot almost entirely non-gas check bullets (as opposed to jacketed) in my .357 - mostly low pressure/velocity loads with no problem. However, I load and shoot heavy loads when desired, using the same bullet and never worry about what little leading might occur.
I also Quench my bullets in cold water as they drop fron the molds.
BUT, bullets which are overly hard can also cause leading if your cylinder throat is under sized and/or your barrel is over sized, and your pressures are not high enough to "bump" the bullet up to bore size when fired.
Give cast bullets a try, but by all means don't stop using them if you show a bit of leading with the first attempts.
I probably have some leading signs in every barrel in which I regularly shoot them, - 38/357, 44 and 45acp - and it sure ain't any big thing, providing it isn't out of control.
Keep em coming!