During my play, I noticed that a level 3 Rocket Hammer deals less damage than a level 3 Sledge Hammer. While in the squad menu, it says Rocket Hammer deals 317 and Sledge Hammer deals 290.
You can try by playing on Mission 13, you're given 1200 Carusaurum at the start, buy a Level 3 Sledge Hammer and test it with the Blasters ahead. One shot from a level 3 Rocket Hammer does not kill a Blaster, while Sledge Hammer does.