One of the major annoyances in CFS3 is the lousy gun ballistics as compared to CFS2 1% fighters.  In CFS2 each type of gun in each fighter can have the correct muzzle velocity as a starting point.  Emmanual Gustin has a table of WWII gun data each nation by type of gun.  See AvHistory web site for a copy.

It appears that MS has one setup for all fighters. Open the Guns XDP file in CFS3 in notepad. You should see 10,750,2. 

Ten represents the rate of fire per second.
750 is MV in meters per second
2 is round time of flight and is the same in CFS2

Set an unrealistic MV such as 2000 in place of 750.  Save. Run CFS3 in dogfight and check the difference in round flight performance.

The correct setting is 870 50 cal; 890 20mm, 835 bb guns US.  10 is ok for 20mm.  12.5 for 50 cal. 

You may want to adjust MV and rate for your favorite fighter.   Or you can refer to the ballistic chart for German or British fighter gun data.

Astute observation.

We are referencing guns and aircraft and not weapons and aircraft folders in CFS3

But

3US_P-51d XDP, aircraft file shows General Allegiance = " "

50calbrowningm2_gun XDP guns, shows General Allegiance = "2"

Which means that 3US reads the defaut gun data.  Not accurate.  750 to 870 50 cal is a HUGE difference in round trajectory.

You are right that each aircraft has gun data.

I am right that the 3US_P_51d doesn't relate to individual gun ballistics data.  I know that from dialing in the correct MPS for the 50's for the 51.

I haven't checked other 3US aircraft.  MV is critical.