Like stated, the 75mm cannon that was mounted on B-25's, both field mods, and later factory builds, were crew-loaded. Loader would unstrap a round, place it in the load tray, ram the round home, close the breach, and let the pilot know that a round was up and ready to fire.
The loader could not do this if the place were pulling any G's to speak of.
If HTC codes in the 75mm, how they address the rate of fire, and loading under G's, will determine in the end how many rounds you could get down range, how accurate, and how many shots per strafing run.
Of note, at least field modified B-25's with 75mm often retired their airframes in about 20 shots fired, as the rivets began to round out (at which point, the plane would become a parts bin).
Also, 75mm equipped B-25's seemed to be best at anti-shipping operations. Sampans, unarmored freighters, trawlers: all part of the effort to isolate and starve out Japanese held islands by stopping all their resupply efforts. Later, many factory equipped 75mm armed B-25's pulled the 75mm out and they field modified them by adding more .50's, as massed numbers of .50's (often with API rounds) proved to be more effective in anti-shipping and other CAS operations.
Also, 20 to 25 rounds was a typical load out for the 75mm cannon.
I think a lot of people think they are getting an uber anti-tank platform with a B-25 equipped with a 75mm cannon. I think they will be sadly disappointed.
