How were Motorkanone sighted in?

[Broncazonk]

Given the effects of gravity, and the required ballistic arc necessay for fired projectiles, how were MG 151/20 motorkanone sighted in? Note the ballistic arcs illustrated in the diagrams below. The arc is achieved by elevating the cannon muzzle in the wing and/or fuselage. But you can't do that with a motorkanone, as the projectile goes straight out of the propellor hub. The muzzle cannot be elevated, and the shell began falling the instant it left the barrel. As a result, a motorkanone must have had a VERY short range.

So how did they sight them in?? That is, how were they harmonized with wing and fuselage armament?

Bronc