*** Posted by run ***
[All fighters should carry a gun whether it be for air or ground use but what size should be carried and what type the two i have seen most in use is the M61 vulcan rotary cannon 20mm and the mauser 27mm cannon . so whats your veiws whats the best, worse and the most powerfull (A-10 30mm .) ]
It all depends on what you are going to use it for. Higher caliber guns make more damage and are the best when dealing with amoured vehicles and other stuff on the ground. Lower calibers are sufficient against air targets.
Lower calibers tends to have a highter rate of fire which is very important when you are trying to kill another fighter doing evasive maneuvers.
Lower calibers are also lighter so you can carry a higher amount of bullets.

Regards Run