send it back !
i tried hornday and cci ammo, they all misfired. i scrubbed the gun down several times to get rid of the factory gunk, nothing helped. at least 5 out 25 shots misfired.
there have been a few 17 sporty's here, mine included, that misfired.
customer service was good on this repair, i had the gun back the next week and it hasn't skipped a beat since.
once it shoots good, you'll love this little gun !
sg