I can never remember which NOT to do. Is it bad to fire copper jacketed bullets after lead (without cleaning) in a revolver or is it the other way around?

There is a rumor that to clean lead deposits just shoot some jacketed bullets. If you have heavy lead deposits you can get very high pressures doing this !!

I think the rule is don't shoot lead after copper without a thorough cleaning. The theory being that lead will bond to the copper.

Gonna wait and see how this goes. But I always thought it was not to shoot copper over lead.....pressure issues

Lead builds up THICK in the bore. As long as more lead is shot, the soft bullets can deform enough to pass, but leave another layer, further constricting the bore. If you shoot a hard copper jacketed bullet into this constriction, well, it is a constricted bore...in extreme cases bad things can happen.

Copper builds up, but as a thin wash, not a thick layer (99.9% of the time...sure enough someone somewhere has built up enough copper to constrict a bore).

That's the theory anyways...I am guilty of using jacketed .38spl loads to clean out the bulk of the leading in my .357 revolvers. I do have a huge safety margin with that combination though. Now I only shoot jacketed/plated. Life is too short to spend it scrubbing lead from barrels!