Auto Cannon vs Hydro-Jet Cannon
Less of a step backwards than many of the mirrors, the Hydro-Jet Cannon sports identical clip size and weight to the Auto-Cannon. AP damage is down slightly, HE damage is up a bit (almost 15%), and Phosphor spread is down noticeably. Autofire accuracy is up noticeably, but Snapshot and Aimed shot accuracy are both down slightly. Firing speed is almost the same. All in all, a fairly decent weapon for your heavy weapons troopers, if you can work around the underwater only restriction.
The HJC-P is considerably inferior to the AC-I as an illumination device for night fighting. Due to the very low burn time of most underwater terrain, the HJC-P is more like a 'spotting round': if the round illuminates targets in the same turn it is fired, you can engage them. If not, darkness returns.