>>2435402It all depends where you are. Guns are completely fine in National parks and in most national forests. State forests and wildlife areas have more specific rules, normally because of hunting regulations. If you have at least a valid small game permit you are fine for the vast majority of parks.
Breaking into abandoned structures is a different game entirely. Open carry is legal in most states but trespassing with a weapon is an entirely different charge. The crackheads you run into aren't going to snitch so you just need to avoid the urbex hipsters.
