I'm not able to answer your rimfire throat question.
Ah, but the cylinder ring on a Bearcat is the result of improper handling. The Ruger Bearcat and New Bearcat load on the "half cock". Standard procedure is to pull the hammer back to half cock to free up the cylinder. Rotate the cylinder and empty/fill the chambers. The Old Model, without the transfer bar mechanism should only be loaded with 5 cartridges and the hammer should be lowered over the empty "6th chamber". The SOP is to empty the cylinder of spent cases, load one chamber, rotate the cylinder to the next chamber but skip it and go one more. Load that chamber, rotate the cylinder and load the next until you have 5 chambers loaded. Now, pull the hammer to full cock then, by restraining the hammer from falling, pull the trigger then gently let that hammer go all the way forward and set over that "skipped" empty chamber. Load one, skip one, load four, pull to full cock and lower the hammer over the empty chamber. NEVER LOWER THE HAMMER TO THE AT REST POSTION FROM FULL COCK. That procedure will drop the cylinder latch and ring the cylinder.
The New Bearcat with it's transfer bar system should be treated the same way, however one doesn't need to leave an empty chamber...
JMHO,
flatgate