Thanks for the l00ting tip ;)

Light howitzer for light vehicles, like vans/technicals/M113.

Heavy howitzer if you want to steal allied bradleys/abramses. I used heavy howitzer to steal them and strykers later in the game :D Though direct shot from heavy howitzer will blow up stryker, be careful.

In Abiquiu you need to fire Abrams HE shell somewhere near light howitzer that you want - with some luck it'll go on fire and after you take it it's much easier. Abrams is kinda awful in damaging alied vehicles.

You definitely killed some allied crew guys. Which weapon/unit is best for that?