Have you considered an AR-15 in .22LR (such as those made by CMMG)?
It's handier than the massive STG-44 .22 and much better made than the potmetal and plastic HK MP5 .22. It's just an AR with a .22LR barrel & bolt, after all - almost all other parts are standard AR. Mags are much cheaper and easier to find, as well (PSA were selling the Black Dog mags for about $15 last week).
Last edited by Fishbed77; February 20, 2013 at 05:20 PM.