Your jamming problem is almost 100% certain to be the magazine(s). High Standards are superb .22 pistols, but they are probably the most finicky pistols made about their magazines. Their magazines are their weakest link. While the original manufacturer closed down a long time ago, there is a new High Standard Company that purchased the manufacturing rights to them and have new production guns available as well as parts. I have only heard good things about their new production pistols. Their web site is:
http://www.highstandard.com
I would like one or two additional magazines for my High Standard and am considering ordering from them.