Fit
yes, you can luck out and find one that just drops in. It's a bit of a crap shoot. Come to think of it, I did this on a fifth revolver, a Colt style cap and ball, I got lucky and the cylinder dropped in.
1. Smith & Wesson Model 28. Had two frames, the first was a no go, for the second frame the second cylinder had too much end play and too much cylinder gap. You can put in a shim and get rid of the end play but I had to get a third frame to get the cylinder gap right.
2. Ruger Blackhawk. New cylinder was too long, comes that way from the factory. I took a few thousandths off the neck only to find I should have taken it off the ratchet. Now it has no cylinder gap. Proves the measurement process is a bit tricky.
3. Ruger Old Army, blue. Had the opportunity to try more than one cylinder, the second one fit OK.
4. Ruger Old Army stainless. Same story on the second cylinder, the original was a tad out of alignment.
Then I got conversion cylinders for the ROA's, had to juggle them around to find which one fit which frame. Lucky to have two shots at a fit.
5. Colt style cap & ball. Got lucky, second cylinder was a drop in.
6. Taurus 44 Special. Didn't try to find a second cylinder, but the original was out of alignment.
I have another S&W with dual cylinders, a factory job.