Lead fouling and the cylinder gap

[JTHunter]

In theory yes, in practice the cylinder would eventually start binding up. The increase in velocity would be minimal.

If the forcing cone is getting leaded up, wouldn't it be more likely that the bullet would be very slightly slowed, allowing more burning powder to blow out the sides in front of the cylinder?

 

[.38 Special]

I don't generally clean the cylinder face beyond wiping it off with WD-40 on a rag. Whether that tends to remove lead fouling, I couldn't say.

I have, on occasion, put tens of thousands of lead bullets through a revolver without cleaning at all. That essentially turns them (and everything near them!) black, but I never experienced any build up on the cylinder face, let alone things like cylinder drag. If I had to guess, I would say that escaping gas tends to scour the cylinder face, thus limiting build-up. My couple of guns aren't exactly a detailed experiment, though.

 

[Anchorite]

If the forcing cone is getting leaded up, wouldn't it be more likely that the bullet would be very slightly slowed, allowing more burning powder to blow out the sides in front of the cylinder?

And a corresponding increase in pressure?

 

[Jonesy814]

Had a new S&W 22lr revolver, K22, M17 that had a .002" gap on 2 chambers. High spots on front of the cylinder.
As it got dirty, the cylinder would bind on the barrel & keep the cylinder from turning. Had my gunsmith face off the front of the 2 high spots, to match other chambers.

Gap should be .004" minimum.

With no gap, there had to be an increase in velocity. My guess.

A friend bought a used 17-3. After 40 rounds or so the cylinder would bind. Turns out the face of the forcing cone wasn’t completely square and the dirty cylinder would drag on the high spot

 

[JTHunter]

And a corresponding increase in pressure?

Not really. Any excess pressure will seek the first opportunity to escape and that would be the gap between the cylinder and cone after the bullet has gone into the cone. That is a problem with nearly all revolvers that pistols don't have as there is no gap between chamber and barrel.