The hunter designation is used only on single actions with the ribbed barrel that is cut for scope rings . They are also roll marked "Hunter" on the top strap.
If you look in FAQ section of the Ruger web site, you will find a scope ring chart that shows all the Ruger rings and what they fit.
I just looked for that chart and could not find it again, BUT, A call to Ruger will sort out what rings you would need. I also have sent rings back to exchange for 30mm and it took a couple weeks to get the new ones back.
I found it!
http://us.yhs4.search.yahoo.com/yhs/search;_ylt=AwrTcdtA1OxTMVcAnzoPxQt.?ei=UTF-8&type=grv_installertech_14_22&rs=0¶m1=1¶m2=sid%3Dca9273403d16c7e6a6c6cb52e229f048%26b%3DFirefox%26ip%3D76.105.207.64%26p%3Dgroovorio%26x%3D00123FC2F320F4F9%26dt%3DS948%26f%3D4%26a%3Dgrv_installertech_14_22&hsimp=yhs-fullyhosted_003&hspart=ironsource&p=ruger+scope+ring+size+chart&rs=5&fr2=rs-bottom