The blaster cannon refers to both a handheld weapon and a mounted weapon.
The handheld weapon is a shotgun weapon used by some types of pilot class in Star Wars: Battlefront. It shoots a random spread of blaster bolts that is extremely deadly at close range, but has a low chance to hit at a longer range.
From point-blank range, the chance to kill is 100%.
The mounted blaster cannon is a powerful blaster weapon that is mounted in turrets and on vehicles. The chance to kill for vehicle-mounted cannons is 100%, and the more powerful ones are able to kill tightly packed groups of enemies.