I have a couple revolvers with both .22LR and .22Mag cylinders -- different makers.

Anyway, why can't I just put the .22Mag cylinder in and shoot .22LR through it?

The headspace[rimthickness] it different on a mag cartridge and the body of the cartridge is slightly larger as is the throat of the mag cly....you might get the LR to shoot but the case might split and blow gas out and the accuracy would be BAD and the cly would get etched at the mouth of the LR case and make the mag shells hard to seat and extract...this would take a lot of shooting but some shell brands/type are worse than others....the lead bullets in LR swell to fit the larger bore made for the mag jacketed bullet and often aren't as accurate as a plain LR gun only....hth..good luck and good safe shooting!!

I had your same question a few years ago when I had two revolvers in the differing calibers. As I recall, the .22LR would not function in the magnum because the rim was too thick to allow the cylinder to close. The magnum stuff would fit into the .22LR cylinder, but the rim was so thin that the firing pin would not reach it and there was then no ignition. Considering the cost of 22Mag ammo (about the same as my reloaded .223s), I sold the mag for a Ruger MkII with the 10" bull barrel and never looked back...

.22 LR uses a heeled bullet (the portion of the bullet inside of the case neck is smaller than the bearing surface outside of the case) so that the outside diameter of the case is the same as the bearing surface diameter of the bullet (about .222"). The .22 WMR uses a conventional bullet of about .224" diameter and the INSIDE diameter of the case matches this, making the outside case diameter somewhat larger.

While you can't shoot 22LR or it's kin in a 22WMR revolver, you can save a bit by shooting 22WRF (Winchesater Rimfire). Just rememeber to clean the chambers well if you want to use 22WMR after firing 22WRF.

I had a cheap but well made german single action revolver with 2 cylinders and I could never get good accuracy with .22 only with the .22 Mag...