I prefer the MK II over the other version as it holds ten rounds, has the firing pin stop, and easier access to the bolt ears through a tapered rear receiver. To me the MK II is the best version of the Ruger .22. That being said there is nothing wrong with a MK I. The MK III has some "features" that have made some problematic like the loaded chamber indicator and magazine disconnect, but these can be overcome with some modifications.
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