My son turned 21 yesterday. I'd presented him with a pistol at Christmas, but his school schedule since has left him little opportunity for shooting. Today, we managed to hit the range for him to put his new pistol through its paces. I brought along my 1983 Colt SAA with its new .44-40 cylinder for a quick functions test. I'd previously assumed that this cylinder would benefit from some chamber honing, as they looked a little rough. But empties fell right out after an initial nudge with the ejector rod. A tight barrel/cylinder gap of about .002 had no ill effect, despite the "conventional wisdom" that a larger gap is optimal for black powder cartridges. The action became a little sluggish after 50 rounds of FFF Olde Eynsford under a 200 gr. PRS Big Lube Mav Dutchman, but that mirrored my experiences tih my late 2nd Gen .45 Colt SAA with BP cartridges.
This cylinder, being in-the-white, presented a photographic opportunity to show how much and where BP fouling deposits itself on the cylinder. So here goes:
I'd assumed that the sluggishness developing in the action was a consequence of my having a tight barrel/cylinder gap of about .002. But then I noticed that my gap remained:
So where was the drag coming from?
It appears that, despite my having set this cylinder up for zero endshake, enough carbon managed to make its way between the cylinder bushing and the frame to initiate drag. When removing the cylinder, some good chunks of carbon fell from the base pin bushing, but I photographed what remained.
Like Driftwood Johnson, I'm becoming suspicious of the claims of a larger barrel/cylinder gap being necessary for shooting blackpowder cartridges in revolvers. Instead, I'm leaning towards the tighter gap producing less fouling and therefore being beneficial. Eventually, enough fouling will make its way between the base pin bushing and the frame (and it took 50 rounds today to do this), but I don't think a larger barrel/cylinder gap ameliorates that at all. Rather, I think that a smaller gap reduces the amount of fouling that blows between the base pin bushing and the frame. That fouling argues for the reliability benefits of greater endshake, but I don't think it supports the maxim of a larger cylinder gap being necessary for BP cartridges. More endshake may require a larger barrel/cylinder gap to keep the cylinder from contacting the barrel breach, which may be where this "rule of thumb" originated.