Whether you have an air rifle for dispatching small game or a large-bore rifle for taking out bears, keeping your riflescope sighted properly is essential. There are several reasons for this, not just the obvious ones of simply being accurate.
First, a good hunter strives to minimize suffering. The point of a shoot is to get a clean kill with minimal bullet expenditure. It's not to cause pain and suffering to an animal. Therefore keeping your rifle sighted ensures that you minimize unnecessary injuries.
Next, consider safety. Hunters need to be able to predict where the shot will land. While this isn't as important with a low-powered rifle, such as an air rifle, it's essential for anything that uses a charge to propel the bullet. A .303 bullet has a killing distance of up to a mile, so if there's nothing to stop the bullet, you don't know where it will land. Keeping your rifle sighted will ensure that you know where that shot will end up every time.
Of course, if you're using the gun to repel a bear or a cougar, that shot needs to be accurate to save your life. If