37mm M3 gun - yep. You can even fire it from the hip! Has AP, HE and shot ammo.
75mm M3 gun - yep. Too heavy to fire by yourself. Has APC and HE ammo.
You can find ammo and cannons in the museum. Ammo can not be crafted now howewer.
To do list:
Balance the 37mm and 75mm guns!
Even more cannons!
M3 Lee Medium Tank vehicle!
Muzzle loading Cannons !