I'm having problems with the main 37mm cannon.... It lobs shells out very slowly, and not very far.... I have experimented endlessly as to a good convergence with the machine guns, but haven't quite found the "sweet spot".... any suggestions??? I usually keep the machine guns at 300.0, and the 37MM at 250.0.... hose with the machine guns and get close and finish with the cannon.... Is it just the 37mm?.. It has tremendous destructive power, but seems to be an abysmal air to air weapon.....

Wow...nothing?

Any weapon shooting through a propeller hub, cannot be calibrated, and its range, trajectory would depend on the shell.
This also goes for guns shooting through the propeller using synch gear.
A BF 109 would be set at 350m.
Hope this helps.
I usually set cannon at 500 m on a 109.

Will try the .500 setting....Thanks!!

The 37mm M1 on the P-39 has such a horrible muzzle velocity and trajectory, I wouldn't fire it any anything farther than 150m. Of course, the great thing about that weapon is that a well-placed shot with one round can be an instant kill.

Thanks, Jarink..... That seems the best way to use this planes guns.... Use the .30's/.50's to wound and then finish with the .37 at close range... Thanks, all.

Jarink is right, this is called "ballistics", the 37mm shell is so heavy that it won't go that far before gradually plunging towards the ground ...

Hartmann, the famous 352 victories German ace used to only open up when he was around 50 m from his targets ...

Another famous German ace (can't remember his name) used to tell newbies something like:

"when you think you are close enough from your target, get closer some more ..."

The closer you fire, the more devastating effect, and the more accuracy ...