Howitzer.

   Up til, or perhaps thru WWII artillery was composed of guns and howitzers.  Guns had longer barrels and longer range.  Howitzers were built the same as guns but had shorter barrels and could elevate them higher than guns.  The shorter barrel made them lighter and easier to move.  Forty five degrees of elevation gives best possible range for artillery. After WWII, since the pieces were mostly the same, parts would interchange, we stopped making much talk about the differences.  The 155mm (6 inch) howitzers we are sending to Ukraine can fire a 95 pound shell a tad more than 7 miles.  I am using figures from “Shells and Shooting” by Willy Ley published way back in 1942.  I am not aware of any technical improvements since then that would increase range or weight of shell much. 

   For artillery fire to do any good at seven miles you need recon to spot your target, and ideally a forward observer to report where the shells are falling and allowing the artillery to correct its aim.  Seven miles is a long way out for recon and a long way to push out forward observers.  The 7 mile range of the 155mm howitzers is probably plenty.