It's the same as the MG counter. Testing offline, I was able to go over the amount of 20mm I was suppose to have by 22 before I had to stop. I haven't had a chance to test if the MG's were empty if the 20mm's would work. The tanks were like this, secondary fire in the turret for many is a machine gun and it would stop maybe 60 short of what it was suppose to be if you had fired that many AP/HE rounds. I haven't been in a tank in a while to see if it's been changed though.
It is the .50s plus the 20mm. The
total count for that position, not the individual guns themselves.
It's the same in fighters. The 190A8 with mixed 30 and 20mm shows only a total for all "primary" or "secondary" guns, not just the 20s or the 30s.
The caveat to this RE: B-29 would be that in the tail gun position the .50cals
are the primary and the 20mm is the secondary (or vise versa, can't remember) and can be fired separately.
wrongway