WW2 tanks typically had a main gun and one or more machine guns. How were they used in combination?
Excerpt by James Doty on Crossfire Discussion Forum
Modern tanks do not fire main gun and coax machine guns simultaneously. It is pretty easy in an M1 or Leopard (and I presume all other modern fire control tanks) to switch between the two. For older tanks, the gunner may have a more involved process in switching (but I don’t think so) but still never engages both at the same time. Loader/TC/hull mounted MGs can be fired at the same time as the MG or coax. MGs are/were not typically used for ranging fire as someone stated earlier because the ballistic characteristics are not the same. If a crew were low on MG rounds and didn’t want to waste one to find out the range of the target, well then maybe you could use the coax to get an estimation.