When I was young, I had a Jennings J22. I never could get it to shoot more than 3 rounds at a time, before it was jammed. I had a Stainless Mark II Target at the time also, so I sold the Jennings and never looked back.
Now why on earth would you want to sell such a fine piece as the J-22? I'm quite certain whatever issues that little gem had were due to user error.
ps...do you think the sucker you sold yours to might want to buy another one?