Yes, they can charge you. To charge someone, there must be "probable cause," or a reasonable basis, for thinking that person committed the offense. If you had the keys to a car--thus could access, drive, etc. it--and a gun is found in it, that can provide a reasonable basis for thinking it is your gun.That's not to say that they will charge you--only that based on what you write, they probably could. It's also not to say that if charged, you will be convicted: more, and more compelling, evidence (proof beyond a "reasonable doubt") is needed to convict. Often, there is enough evidence to charge someone with a crime, but not enough to convict: to use a famous example, take OJ Simpson. There was enough evidence to charge him and put him on trial; there was not enough to convict. In this case, your access to the car *could* provide enough to charge, but they would likely need more (e.g. your fingerprints on the gun) to convict.