I noticed two things incorrect with the 35mm: first, the muzzle velocity is wrong, in game, it is 1440 m/s.

However, in real life, that is the velocity for APDS shells, not the regular explosive shells (the ones used in the game), which have a muzzle velocity of 1175 m/s. So, first things first, muzzle velocity should be corrected.

The second thing is more complicated, the ballistics. Currently, the Oerlikon 35mm cannon shells have the same airFriction as 7.62x51mm bullets. In real life, the far larger cannon rounds have far superior aerodynamics.

Current airFrictions:

7.62x51mm = -0.00096
35mm shell = -0.00096, same!

The "correct" airFriction for a bullet or shell is determined by comparing in-game time of flight and/or velocities to real life figures. The real life figures for the Oerlikon 35mm firing high explosive shells are:

High Explosive Incendiary at muzzle velocity 1175 m/s
1000m = 1.0 sec
2000m = 2.2 sec
3000m = 3.8 sec

And the average of the three in-game airFrictions which result in those times of flight is:

HEI = -0.000245

So, in summary:

-Change 35mm muzzle velocity to the correct 1175 m/s
-Change 35mm airFriction to a realistic value, in the range of -0.00024-0.00025 (or thereabouts)