OK - might be 22", that looks like what they come in from the factory. It is the original Ruger barrel.
No gunsmithing work to it, it is as it came from Ruger. It has fired less than 100 rounds.
Here is a link to pictures/ad:
http://www.gunlistings.org/iowa-gun-classifieds/ames/rifles/122048/ruger_m77_mark_ii_left_hand_3006
