[Unclenick]

I think it is more gas cut splatter than condensing vapor. May be partly liquid, but I think it's more like a pile of fine spitballs building up. I say that because I put a sight extension on a bull-barrel target pistol that overhangs the muzzle, where gas temperatures are much lower, but it quickly picked up an even thicker cake of lead above the muzzle than my revolvers ever get. Vaporized lead becomes mostly oxide, I expect, and forms part of the white cloud of smoke. Don't want to breath it, whatever form it gets there in.

As to the lead's appearance on the side of the cylinder, it will likely have deflected from the top strap accumulation that Scorch mentioned. I haven't seen it appear at that particular place on my guns. While I doubt it is significant, I would use a feeler gauge to check the barrel/cylinder gap, just to make sure it isn't too wide for best accuracy. Should be in the 0.004"-0.006" range, typically.