This could could also be added as a modification to existing A6M3 in the game unless there were any other modifications done.
If we can find a similar aircraft to carry and disprove the current conclusions, I think it’s acceptable, because presumably, from the number of bullets in the A7M3-J, the J2M5 should have the same number of them( 60 rounds)
A7M3-J is the only one, though it’s a good example, since both inboard and outboard guns went from 200 to 60rpg.