big blue -
pack it up, ship it back, and they will fix it.
it was really frustrating for me, i waited about 4 weeks to get my 17 sporty and then it mis-fires. i went through boxes of hornady and cci, cleaned it, scrubbed it, talked nice to it, pointed it towards mecca, and it still misfired. the dents in the rimfire rim were really wimpy, the dents my my 20+ year old marlin 60 makes are deep and very well defined, the sporty, shallow and inconsistant. it went back and within a week, or so, my 17 was back and no misfires !
sorry to hear about it !
sg