after substantial research, I have learned that the ha-go (boat) potato launcher HEAT shell actually fucking sucks despite having substantially more explosive mass (and lower velocity to go with it) than the normal HE shell because HE and HEAT apply the explosive mass to totally different damage calculations and HEAT does NOT apply whatever amount of explosive mass/energy that doesn't go into the jet into the normal HE mechanics like you would expect but has its own different shitty thing that sucks, so if for whatever reason you are playing this shit just take normal HE and APHE if you need pen
you can also uncover this information by just shooting like 3 test shots in the damage view instead of digging through all the files too