Nicked from elsewhere:
MauserWerke GmbH BK-27
At only 100kg this cannon offers a significant firing velocity combined with a relatively large shell, it compares extremely favourably with its counterparts. When compared to the U.S. M-61 with a rate of fire of 6000 shells per minute, the BK-27 seems outclassed with a low 1700 shells per minute. However looks can be deceptive, while the M-61 takes almost a second to reach its full firing rate the BK-27's is almost instantaneous. The Mauser will have fired over 4kg of projectiles in 0.5 seconds while the M-61 scores around 2kg. The M-61 will only exceed the BK-27 after a full second of firing.