K31's are awesome guns. I just made up some handloads for mine if you saw my other thread. Only thing to be careful for is your OAL if reloading for it. Otherwise GP-11 or even the Prvi factory shoots great in these rifles. As everyone said, looks for matching parts, good wood condition, a smooth action, and no cracks in the plastic bolt knobs. Also, if you can unscrew the buttplate, you can check for a soldier tag in the back that shows all the information about the soldier who carried that particular rifle. Some guys have even contacted the original owners and/or their family. Have fun choosing!