I assume the 20mm Gatling Cannon used within the buzzard jet is based upon the 20mm M61 Vulcan, which is the standard cannon used on the F-15, F-16, and F-18. Therefore, the damage and splash damage feels very under-powered as it is nearly impossible to destroy multiple enemy squads packed within a small radius as seen here: http://www.youtube.com/watch?v=J0hyd5R0pFM

The rate of fire is also awfully unrealistic as I calculated the in-game rate of fire to be approximately 680 rounds per minute. The M61 Vulcan has a rate or fire of 6,000 to 6,600 rounds per minute
(source: http://en.wikipedia.org/wiki/M61_Vulcan)

The in-game cannon just doesn't seem to come close to the sheer power the M61 vulcan as seen by this actual strafing run from an F-18: http://www.youtube.com/watch?v=jJoY5V0O7jU

In conclusion, my recommendations are to increase the the damage and splash damage of the in-game cannon, increase the rate of fire to either 6,000 or 6,600 rounds per minute, and increasing the bullet spread to add realism due to aerodynamic effects.