J-1 semi-autonomous proton cannon

The Proton cannon was a long-range artillery weapon used by the Confederacy of Independent Systems during the Clone Wars.

Characteristics
The gun was operated by one B1 battle droid in a side-seat. It didn't have an automatic reloading chamber, so shells had to be manually loaded by at least two battle droids before each shot. The shells packed enough punch that a single hit could deal considerable damage to an Acclamator-class assault ship or completely destroy a LAAT/i.

The artillery piece was mounted on top of four legs, similar to those of Advanced dwarf spider droids, which allowed it to move around the battlefield, though its turn rate was considerably slow.