Another reason, that I haven't seen mentioned as yet, involving the shooting of .22 Short ammunition in Ruger Mark pistols, or any other firearm, that has a .22 Long Rifle chamber, is what can happen with a steady diet of those Short rounds.
Consider, the .22 Short cartridge case is shorter, so the case mouth is closer to the bolt face also. A steady diet of .22 Shorts will have the front end of the cartridge case, after the bullet leaves, create a burn, or carbon ring at that place in the chamber. If that goes on for some time, without some attention with a bronze bristle brush, that carbon ring will hinder a full length .22 Long Rifle round from fully chambering at the time you need it to.
So, for those who think that cleaning a .22 caliber rifle should only be done during "Leap Year's" February 29th day, you just might have a problem developing.