I have a 397 (.177 if it makes a difference), that has started leaking air. I used to be able to pump it up and sit down and wait for a rat or squirrel to come around, but never left it pumped up for more than an hour or so. It used to hold a full charge for said hour without losing power. Well, I went pout for a rat killing spree the other night, and after about 10 minutes, I see one scurrying across my garden. I line up the sights, squeeze the trigger, and the pellet barely cleared the muzzle. Ok, it wasn't that slow, but it was comparable to an old Marksman BB pistol I have which supposedly shoots at about 200fps. I tried it today, and the rifle did the same thing after a 10 minute wait. It works fine for a practice session if I pump it up, load it, and fire immediately, but for hunting purposes, this rifle seems to be toast. Having said that, I hope that someone here knows how I can fix it. I expect to have to spend some money, but obviously, if the fix is more expensive than a new one, then I would obviously just get a new one. The rifle was bought new 5-6 years ago, so out of warranty, but not what I would call old either. Any guidance y'all can give me is appreciated, so any ideas?