I can hit BUFFS and kill them with everything from 7.7mm BBs to 75mm punkins' (sometimes even landing afterward), EXCEPT the blasted 30mm!

I keep all my guns set between d350 & d450 and know where the rounds will go for a given weapon type. What I would like to know is: should I
decrease the convergence on the 30mm and flatten the trajectory or
increase the range and lead more to allow for the lumbering flight of the taters?