Bolt drop is determined by the interaction between the leg of the bolt riding on the cam on the hammer.
Reducing bolt spring pressure well lower the bolt a very small amount, SG's method. Changing the position of the bolt leg well do the same, denster's method.
It's fairly common to see the bolt return spring to have more pressure than it needs. This well dent/peen the cylinder and sometimes cause a drag line.
It's not uncommon to have to tweak both those parts to get a nice smooth action.