Heavy Cannon vs Auto Cannon

• The Heavy Cannon in general has 50% better firepower (effective damage per turn) than the AutoCannon against lightly armoured targets. This advantage increases further against more heavily armoured targets.
• The HC is significantly cheaper to own and operate than the AutoCannon - around half price.
• HC is superior in reaction fire (snap fire) firepower.
• Generally the HC has the best first-shot-kill probability - very important when aliens can reaction fire with plasma weapons on Auto against lightly armoured troops!
• Heavy Cannon is the best starting sniper weapon vs well armoured targets. The Pistol is better, but only against lightly armoured targets. The HC is superior to all others in this regard, even the Laser Pistol. It is only beaten when the Laser Rifle appears.
• HC generally has much greater terrain-clearing capabilities than AC (both AP and HE). HC will tend to destroy objects that the AC would not. However, the AC on Auto-Fire will cover a greater area destruction.
• The HC can step up to tackling Mutons, with some degree of success. HC-AP has double the Autocannon's effective firepower against Mutons, and HE (the best round vs Mutons) is 20-40% more powerful (20% vs AC auto, 40% vs AC snap).
• AC-HE or AC-AP on auto is so inaccurate as to be barely more effective than snap shot. HC snap fire is much more effective than AC snap or auto.

Actually, auto fire with the AC is just as effective as snap fire with the HC until you get past (roughly) 20 spaces from your target (see Firing Accuracy Testing). The firepower ratings given on the firepower table are most accurate at that range. So, anything closer than 20 spaces is going to actually give a benefit to the AC on auto fire.

• However in the rare cases where AC-HE auto can be used without regard to accuracy (point blank range in Power Armour, or short range with targets against a strong wall), total firepower is about 60% higher than HC-HE.
• Similiar to the walls, HEIGHT makes Autocannnons with HE much more powerful. Shooting from higher ground/ Flying Armor will turn an Autocannon with HE into an extremely deadly weapon.However, it has the side-effect of destroying a lot of precious alien equipment, when an enemy dies from the first shot, drops his equipment and corpse, and the 2nd shot wipes out all the bounty.

• Actually, since plasma weapons(the most valuable alien items) are difficult to destroy, this isn't as big an issue as it may seem, since the Auto Cannon can do 44 damage at ground zero, a dead on hit on the killed alien will still leave its primary weapon, since damage vs. objects is not randomized. At one space away, the Blaster Launcher will also survive. However, the body, any grenades, and any spare clips will be destroyed unless your soldier botches the shot by 3 squares or more(2 squares for the body.) Arrow Quivershaft 14:19, 16 February 2009 (CST)

• The main advantages the Auto Cannon has over the HC are its 2.33 times greater ammo capacity.
• Conversely the main downside of the HC is the 6-rd ammo limitation, and its implications for Encumbrance, total ammo capacity, diversity of ammo types per soldier, inventory slots used, and use of the 80-item limit. For small squads (eg 6 man) this will lead to Weight/Encumbrance problems carrying enough ammo to finish the mission. For large squads (14 man) this is less of a problem but still puts quite a strain on the 80-item limit.
• The AutoCannon has definite specialist roles where it is superior to the HC, such as illuminating with IC. AC-HE on auto can also be more effective for mass clearance of deep (but light) cover.

• If using the Incendiary Exploit, the Autocannon gains relative to the HC, as it can fire more rounds (doing fire damage to multiple units each time), and arguably it can make more effective use of the limited number of map squares that can be on fire, due to its smaller burst radius.

• The biggest drawback to all heavy weapons is weight restrictions or the resulting TU penalty from encumbrance. For the HC 81% of starting rookies can carry it (unencumbered) with 1 extra clip, 52% with 2 extra clips and 24% with 3 extra clips. (The first clip of any weapon, usually AP, is loaded automatically and "weight free" during the Equip Troops phase, unless you change or unload it ). As for the Auto-Cannon, 81% can carry it with 1 more clip, 57% with 2 more clips and 33% with 3 more clips.

Note:

"Firepower" as used here is defined as "average armour-adjusted damage delivered on target per unit of time".