A Jennings J22 is hardly what I'd call a good gun for a beginner. They're hit and miss in quality and reliability and frankly I'm not a fan of the ergonomics - they're too small to learn how to shoot with.
If its all you've got then go with it but really I would strongly suggest getting a Ruger Mk II or Mk III. They can be found relatively inexpensively and will provide you with much better reliability and shootability than the J22.
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