Mortar vs Fighter

Movies sometimes test our credibility.
Sometimes this is because the makers do not know better.
Other times it is dramatic licence were inconvenient reality is ignored in favour of the story. We are all used to six guns and double barrelled shotguns firing a dozen times without reloading.
The other night I saw an example of this that was just jaw dropping.
The movie was called Reign of Gargoyles. It was a World War Two story where Nazis bring gargoyles to life and they run amok, attacking B-17s and anything else.
That storyline is not the incredible bit!

There is a scene when the heroes are being strafed by a German fighter aircraft.
The young hero runs out to lure the fighter in close and his comrades then shoot the fighter down.
With a mortar!
Better still, one character is asked beforehand if he can shoot the plane down with a mortar and answers he can if it is drawn down low.
For those of you not familiar with heavier weapons, a mortar of the type shown would have had a muzzle velocity of about 150 m/s. Actual flight speed would be lower and mortars have a very slow, curved trajectory.
Flying at low level, the German fighter might not be moving at maximum speed, but probably be travelling at least 150 m/s itself.
Add into this the firer’s reaction time and the delay while the mortar bomb drops down the tube to fire, and you will see that it would actually be easier to hit the aircraft with a thrown baseball.
The odd thing is, a couple of weeks back I did come across an anti-aircraft mortar round from World War 2. (the movie uses a standard HE bomb)

This round ejects an aerial mine consisting of an explosive charge on a long cord suspended from a parachute.