Technically there can't be less than zero tolerance in the barrel cylinder gap or the cylinder couldn't rotate at all, but what you're describing does sound very, very tight. An ideal b/c gap is between .004 and .006 as measured by a feeler gauge. .003 or .002 and you get the kind of binding you're describing after firing a few rounds; powder residue essentially closes the gap. .001 or less and the cylinder can bind even when clean.
Are you sure this is the issue? It would be strange that the piece once shot normally but now binds; b/c gap doesn't narrow on its own over time, on the contrary, actually, with regular use -- otherwise it stays the same.
Have you measured the gap? If you have feeler gauges, with the cylinder engaged in the frame, pull the cylinder back as far as it will go and insert the gauges from the left between the barrel and the cylinder; the last gauge that will slip between them before the first gauge that won't is the measurement of the b/c gap. Do this for each chamber, because there can be a little variation between them (or a lot, if something's out of true).
This will give you a better idea if b/c binding is really the issue.
In the meantime, stop dry firing to "loosen" things -- if something's binding that shouldn't be, drying firing will just cause damage.
When you stripped and cleaned the piece, did you do a thorough detail strip? Taking the plate off and removing the parts, and breaking down the components of the cylinder, too? If not, it's possible there's some small bit of crud, varnish or even rust that might account for the binding. Take the thing entirely apart and give it a good looking over and cleaning with a gun-specific cleaner.
