Good idea, I second that, but not against fixed targets. In the air you are moving at some speed, and the con is also moving at some speed.
There are some points to consider here because if you set up cnv at 350 yards and shoot with the con at 350 yards, once the bullets converge at 350 yards the con will have traveled 400 yards or more, so it will be away your cnv range.
To setup a gun test bed, a good idea could be as follows:
1 - Select own plane and target plane.
2 - Select speed of own plane and speed or target.
3 - Select separation to target in yards
4 - Select altitude.
5 - click "GUNNERY TEST" button.
Then you and the target are summoned at the selected alt, distance and speed and you can start firing. The target is summoned at your 12, coalt and flying straight ahead.
Once you click the "Back to tower" button, a statistics window is shown, listing information about % of hit with each kind of weapon (Ex. internal guns, MGs, external guns, etc).