I agree with Eric on this one....sparrows are annoying...and you should try some different pellets. JSB jumbo exact 15.8gr shoot very good in everything I own...as long as it's .22cal...can't get them to chamber in the .177 for some reason.

Measure the heads on a half dozen or so of the pellets you have....I've done this with a tin of gamo magnums with interesting (and widely varied) results. Not surprising they shoot like crap.

Al