There was (is) a PC game called Scorched Earth that was like that... Not sure of the name of any 2600 game that fits the description.
Scourched Earth from what I found is kinda like Atari's Combat only with better graphics.....
Baron,
Are you driving tanks in that game?
if so your answer is Combat
Err... no. Combat didn't have turns, didn't have power controls, and only debatably had trajectory controls.
The ONLY 2600 game I know where players "controlled cannons and had to choose range and hight of there shot" was Human Cannonball.
But you didn't shoot at each other in that game.
You shot a human into a tank of water(if your projectile was lucky and you weren't on a sick "bounce him off the wall" kick).