Froggie,
You are correct to question the pawl, I'm sorry, I completely neglected to address it. Perhaps because fortunately, it's a non-issue in the situation discussed above; changing to a cyl with less chambers. I posted the attached recently in another thread about the feasibility of adding a 6 or 9 shot mag auxiliary 22 mag cyl to a 22 LR Single 10:
Using Convertible cylinders with less chambers:
When cyl chamber count increases, like from 6 to 10, or 9 to 10, the cyl hand (pawl) is required to be slightly shorter because the cylinder doesn't have to be rotated as far from one chamber to the next; 60 degrees to 36 degrees and 40 degrees to 36 degrees respectively. And the shape of the teeth on the hand become more critical (please see photo below). Therefore, cyls with less chambers will most always work in guns with hands fitted for cyls with more chambers.
I say, “most always” because there's no rule, and all parts have some variations. But most hammers will over travel enough in the grip frame slot to push a cylinder with less chambers far enough to lock up in line with the barrel, and therefore it's perfectly safe to shoot. That's all there is to it. In an 8 or 10 shot gun, for example, the hammer will move far enough to the rear for a cyl with less chambers to lock up in line with the barrel. The cyl usually won't lock up until after the full cock click which is not ideal timing but it's safe and it works! That's better than the cyl locking before the full cock click, or the hammer could not be cocked w/o forcing it and binding the cyl, if at all. Of course Ideal timing is when cyl lock up occurs simultaneously with the full cock click, but not required and many Rugers come from the factory when this is not the case.
So in summary, a cyl locking up before the hammer cocks is what ‘can’ occur when using a cyl with more chambers in a gun with cyl of a lesser number of chambers, and it’s because the pawl is longer. But it should be tried before saying it ‘won’t’ work. Also the 2nd tooth length on the hand can be “compromised” to work with both a 6 shot and 8 shot cyl.
The next logical question is how do those aftermarket 8 shot 22 cylinders “drop in” and work as advertised in 6 shot Rugers. The reason the 8 shot cylinders work in 6 shot revolvers is because the cyl rotation difference between chambers for the 8 shot cyl of 45 degrees, is closer to the 60 degrees of the 6 shot cyl, than the 40 degrees of rotation for a 9 shot, and much closer than the 36 degrees of a 10 shot cyl.
In addition the aftermarket 8 shot cylinders may have the ratchet notches on the cyl cut with a bit more tolerance for the longer 6 shot hand. Which in turn creates more tolerance in the hammer travel so it can reach full cock without the 8 shot cyl rotating the full 60 degrees of the 6 shot.
Notice the bottom tooth of the 10 shot cyl hand (pawl) on left is shorter (and shaped more precisely) than the 6 shot pawl on the right:
Note: As with all cylinder swaps, the main issue of concern is overall cyl length. Is it too long or too short to fit the cyl window? Too long is simple, dress down the gas ring on the front of the cyl to fit the frame.
Recognize, the 30 carbine cyl presents a great opportunity to turn a larger frame 327 into a convertible 32-20 as well, when re-chambered to 327! Note that an OM 30 Carbine cyl requires a 32-20 rim size chamber recess because the rim is about .050” larger than the 327 rim. See post below.
Hope this helps,