Not sure what you're trying to say. The BK5 was a 50mm round. The MK108 was a 30mm round with all of 1600 fps muzzle velocity. The MK103 was a 30mm round with something like 2800 fps muzzle velocity. Both were smaller than the BK5, though the high velocity of the MK103 would be nice if you're actually trying to hit a moving target, unlike the MK108 that has something like a 50 foot drop at 800 yards.
Yes, but when you consider;
4/5 times, a single hit from a 30mm will bring down a fighter.
5-10 30mm hits will usually bring down a bomber.
Now, out of pure speculation, lets say that a 50mm round will be 3x more powerful than a 30mm round (as modeled in game, in general, a 30mm round is approximately 3x as powerful as a 20mm round, which is 3x as powerful as a .50 cal round, which is 3x as powerful as a .30 cal round (
Source).
So... we'll standardize a 30mm hit to one and a 50mm hit to three.
The BK5 has an ROF of 45 rounds per minute.
The Mk103 has an ROF of 380 rounds per minute.
In one minute of sustained fire, a BK5 would cause equal damage to 135 30mm hits.
1 Mk103 alone churns out 380 RPM, and the Me410 in this configuration has two Mk103s.... so it produces 5.6 times as more firepower from the Mk103s as from the BK5.
Thus my belief that the Mk103 is more significant in the Me410's armament than the BK5