I think headspace consideration in a revolver is.different from other designs. Misfire is more of a concern than brass life. The pressure is too low for the brass to cling on the chamber. In fact the brass can't cling on the chamber. The donut on the ratchet can take that sort of beating. Instead the brass is supposed to slide back and "lean" on the frame.
Headspace consideration is the same in a revolver as anything else. For rimmed rounds, that the space the case rim fits into.
Reliable ignition is ALWAYS more important than case life. I can't think of any firearm design where reloading case life is a high priority, and can think of more than a few where it is of no concern at all. Reliable ignition, on the other hand is always a top priority.
Case pressure in revolver (and all other) rounds is not "too low for the brass to cling to the chamber and seal. That should be obvious, we don't get gas coming BACK at us
What makes the revolver unique is the fact that the cases are not held tightly in the chamber by a boltface /breechblock. The case is literally, free to move backward, until stopped by the recoil shield. And that is what happens. Primer ignites, powder burns, and as the pressure builds, (pushing in all directions) the case, being lighter than the bullet and having less inertia gets pushed back until stopped by the recoil shield. At that point the pressure can only push the case walls out so they seal against the chamber wall as the bullet begins moving forward.
As the bullet heads downrange, and the pressure drops, the natural elasticity of the brass results in it springing back away from the chamber walls so it will extract freely.
The spent brass come out of the cylinder with a gentle pull of the extractor star. No primary extraction is needed. However it is different story if the same round is fired in a lever action rifle. More mechanical advantage is needed to extract the spent brass. Hmm... How does it work?
Its not really a different story when a revolver round is fired in a lever action rifle. The case is still pushed back by the initial pressure build up, but since the bolt face is right up against it, there's no where for it to go, so it doesn't move, it just transfers the force to the boltface. The other difference is the slightly longer time it takes the bullet to clear the muzzle and vent the system pressure. Everything else is the same.
take a good look at the typical Marlin/Winchester type lever actions. They don't have "powerful primary extraction". Nothing like the camming action of a turnbolt rifle. Its not needed, even for the rifle rounds you find in those kinds of actions, and more than enough for lower pressure pistol rounds. Yes, the lever linkage does amplify the amount of force pulling the fired case out, but its also a necessity in order to operate the (relatively) "heavy" bolt mechanism.
Every system has a pressure limit within which it operates properly and when exceeded cases stick in the chamber, because they have been pressed HARD against the chamber walls and that extra "pressure hammer" reduces the effectiveness of the brass springing back. Run too much pressure in a lever gun, and despite its more "powerful" extraction cases WILL stick.
I know its frustrating when the brass you want isn't currently in the major supply chain outlets, and can't be easily made from brass that is available.
There is something you can do, but its time consuming costs a bit, and there's no guarantee of success. If you have the time, travel abit. Get away from larger towns and check out the small ones, especially the ones close to "hunting country", and visit the small "mom & pop" type stores, Gun shops (of course) but also Hardware stores, grocery/sundries stores even old gas stations. Places that were running before the Internet, and aren't chain franchises, etc..
Sometimes you can find some old, and odd ammo that's been sitting on one of their shelves for decades. If you get lucky you might find something you can use, and if you get REALLY lucky, they'll sell it to you for the price marked on the box!
My personal best score in that direction was I once found a 25rnd box of Winchester 12 ga 00 buck, in an old hardware store, which they happily sold me for the $4.95 price written on the box!
You MIGHT find a box of .25-20 at such a place. Wouldn't be cost effective to go looking just for that, but if something takes you near those kinds of places, taking the time to look might just pay off, though you do have to "kiss a LOT of frogs before you find a prince"
