Calculating the Reload Time of Advanced Cannons

hi,
i'm new to the game and i'm having some issues on calculating the reload time of Advanced Cannons.
i know it depends on the amount of autoloaders and the cool down time of the barrel.
i also know, that the ammo controller show the stats for my shells.
my problem now is:
the autoloader (1x 2m autoloader, 1x 2m shell rack and 1 feeder) in my test gun loads the shells around a 1/3 faster as it should and i don't know why