Quad Cannon Snipe Rounds upgrades are available for $500 at Prince Kassad's Palaces (only in campaign). Quad Cannons can kill an infantry with a single shot like a sniper but this ability will not work on anything else. It is presumed that, originally, Kassad was to have sniper rounds in his Main Faction, but they were most likely cut because it instantly kills infantry in one shot, it would make the Kassad quad cannons (upgraded with Quad Cannon Snipe Rounds) very strong against infantry, but unbalanced and overpowered at the same time.