Legal Question in Criminal Law in Pennsylvania

It can be, depending on the facts. But fingerprints are not the only kind of evidence prosecutors can use to prove you possessed the gun. To take the most obvious example, if a police officer testifies she found the gun on you when doing a pat-down, that would be more than enough to support a conviction.

It's surprisingly uncommon for people to leave fingerprints on guns, so even if you didn't leave any it would mean only that one particular type of evidence doesn't help the prosecution.