I'm bumping this super-old thread to add some info, as I'm just encountering this now.
I have Iowegan's Book of Knowledge on the Mk. II pistols. I went to replace the worn extractor and file a flat on it per Iowegan's suggestion. Upon disassembly, I found the firing pin stop hard to remove. Reading more in the book I found that bending of the pin is caused by dry firing.
You won't damage the chamber, because of the stop pin. Yes, you have to dry fire it to disassemble, but dry firing other than that will eventually bend that pin. Better to use snap caps than to screw around and bend the pin.
Iowegan says a new stop pin can be made from a 1/16" drill bit. I *think* he also said it's the same pin as in the 10/22, but don't quote me on that; I'll have to double-check. 10/22 pins are easily available, while Mk. II parts are being slowly discontinued.
Also, Ruger Mk. III and newer pistols use a roll pin not a solid pin. Maybe that will hold up better to dry firing, as it has room to spring back?
I can't seem to find the buggers in stock anywhere, so I'm going to see if a 1/16" drill bit does indeed fit. If so, I'll make my own pin out of it with a Dremel cut-off wheel.