Hop up does not effect 280+fps guns until past 10m, so your gun is shooting low because your sights are off.
Set a target at 40m, turn your hop up MOSTLY off, fire, watch it drop. Increase hop a half turn. Fire, watch it drop, adjust accordingly until it flies straight. once Straight, over hop a little to make the bb rise a little, fall and then rise a little more in flight.
Once done. Adjust your sights so you shoot where you aim.
Ár skal rísa, sá er annars vill
fé eða fjör hafa. Sjaldan liggjandi úlfur
lær um getur né sofandi maður sigur.