Originally Posted by SultanOfShwing
By not necessary, I meant that I probably won't need to change anything because it should already be optimized because it is a used gun.
Hop-up changes. You will probably need to do minor adjustments depending on atmospheric conditions, and when one cleans the barrel it's usually a really good idea to dial it off. M16-style hop-ups are also known to not hold their position.
Hop-up isn't static. Get used to playing with it.