Overheating

""Heat level critical. Shutdown imminent.""

- On-board computer, Mechwarrior 2

Some games give you unlimited ammo, but the designer doesn't want you to fire continuously, so your gun will overheat if you fire continuously for too long, and you have to wait for it to cool down before you can use it again. Alternately, you may have to reload, but have unlimited magazines, which is functionally identical. This doesn't just apply to guns. For example, in Excitebike, the motorcycle will overheat if you go fast for too long.

A particularly bizarre version can occur in games that feature mounted and handheld versions of the same machine gun, which may be governed by totally separate rules; for example, one may require reloading while the other does not but is able to overheat. Real mounted weapons often have rather obvious and bulky extra cooling hardware installed, though this is rarely reflected in-game.

This can be partly considered an example of Truth in Television, as the dissipation of waste heat from various forms of technology is a major design consideration that is often overlooked; however, in video games the effect is typically exaggerated by a variable margin in terms of speed and grossly under-exaggerated in terms of severity; overheating a machine gun will typically cause it to steam as if it has a water jacket, without the risk of rounds spontaneously igniting (known as "cooking off") or permanent barrel damage that come with overheating a real gun. May be partially justified by having the overheat meter represent a safety threshold imposed by an automated weapon control system or the shooter himself, and not the absolute maximum temperature at which the weapon is capable of firing. However, keeping firing at the risk of weapon damage is generally not an option. Typically, the quick-change barrels of modern machine guns are not represented either, and there is no way to deal with an overheated barrel but wait for it to cool back down (which, for gameplay reasons, happens surprisingly fast).

Gatling Guns, especially of the modern Minigun variety, often fall victim to this trope, despite the fact that their multiple rotating barrels is a special design meant to avoid overheating.

Essentially an inverted Charge Meter, and similar in function to a Sprint Meter, though the latter will generally go down instead of up.

Video Games

 * Happens with Covenant weapons in Halo that don't have to be reloaded. Those weapons also need to be replaced after they run out of ammo.
 * Same thing in the fan game Halo Zero.
 * Mounted machine guns function this way in Reach. When mounted, they overheat, but when torn free, they can be fired nonstop until their ammo runs out.
 * The beam laser in Forsaken breaks if it overheats.
 * In the shooter minigame in Final Fantasy VII the laser becomes less and less powerful if used continuously and you must wait for it to recharge.
 * Many of the guns in Star Wars: Battlefront follow this trope. Your backup pistol has unlimited ammo, but overheats quite quickly (and has less power than any other weapon in the game, so using it is ill-advised); vehicle-based weapons all have some sort of heat meter, and the Clone Commander's chaingun in Battlefront II uses the overheating mechanic to avoid becoming a Game Breaker.
 * Happens in Mass Effect: All guns use 'mass-accelerator' technology to shear off a piece from a block of metal inside the gun and accelerate it when fired. As the technology only needs a small piece to have a lethal amount of force, this allows guns' blocks of metal to be sufficient to fire thousands of shots and culminates in ammunition being a non-issue in-game - guns still generate heat though, and thusly creating the Overheating system inside the game. Certain upgrades and ammunition will increase the rate at which the guns overheat, others will lower it.
 * Though it should be noted that with adequate equipment, you can easily make it so the guns will never overheat. Alternately, make it take a very long time to overheat and add some firepower. The Infiltrator class has the ability to lower the heat output on firing weapons which when combined with damage upgrades makes the class output the most damage over time in the game.
 * It is, however, thoroughly impossible to do so with any weapon using High Explosive Rounds, as they generate +500% heat.
 * Alternatively, go the other way and cram on extra-heat, extra-damage mods onto your Sniper Rifle and accept the fact it'll overheat after every shot, essentially making the equivalent of a cannon. Which begs the question: aren't any parts being damaged by being subjected to +550% over standard heat on a regular basis?
 * Mass Effect 2 went for a system that works like a typical shooter with limited shots before reloading. They attempt to reduce the degree of Retcon by explaining it as ejecting the heat sink of your gun and inserting a new one. Which, naturally, should prevent you from reloading single shots into a gun that fires multiple shots per heatsink... but doesn't. And while it would make sense to be able to wait for the heat sinks to cool and use them again instead of throwing them all away and trying to scavenge new ones, that's not an option. Of course, all this only applies to you. Computer-controlled characters still have Bottomless Magazines. Gameplay and Story Segregation is in full effect here.
 * In the Mechwarrior games, this is an inherent gameplay trait. All weapons create heat that must be dissipated by your 'Mech, but energy and missile weapons cause the most heat. Heat sinks can help dissipate the heat generated, but there's still a danger of overheating, and once you pass a certain threshold the 'Mech engages an automatic shutdown. If you override this automatic shutdown, you run the risk of ammunition explosions and reactor meltdowns.
 * However, that really applies only to energy and missile weapons: ballistic weapons generate (almost) no heat at all, the only exception being the gatling-style Rotary AutoCannon, which overheat distressingly quickly.
 * This is an important part of the Competitive Balance of the various weapons, usually weighed against its ammo stock: laser weapons have Bottomless Magazines but build up heat quickly, making them ideal for a long but low-intensity fight, whereas ballistic weapons had little heat buildup and fired rapidly, but ran out of ammo in a longer engagement. In addition, a mech could spend tonnage on "heat sinks" that increased the rate it cooled down at, allowing it to mitigate the heat of its weapons at the cost of having fewer of them.
 * The Sten and Venom of Return to Castle Wolfenstein are rare examples of overheating weapons that still have limited ammo.
 * Yoshis Safari had the, uhm, Super Scope overheat.
 * The mounted guns in Left 4 Dead use this. They get red hot fairly quickly too.
 * They're also bloody inaccurate, meaning precision shooting is impossible. But the over heating makes effective More Dakka pray and spraying impossible as well, thus rendering the mounted guns Awesome but Impractical.
 * To elaborate, the mounted gun takes twenty seconds of continuous fire to overheat. Twenty seconds seems short, but it's a rather long time in fast paced video games. Its real weakness is the limited firing arc and the position of the gun, as well as taking about a minute to cool down once they overheat.
 * Time Splitters and its sequels use this with the chain gun and plasma rifle, among others. The former even allows you to keep the barrel constantly rotating without firing (which keeps the heat gauge on about 1/3) so you can start shooting more quickly at the cost of overheating faster.
 * The vehicles in Prototype have their machinegun/miniguns do this (they have infinite ammo in missions where you need to use the vehicles or lose).
 * Each character's built-in guns in Capcom's Alien vs. Predator Beat'Em Up could overheat, but recharged over time. Except for Linn Kurosawa's, which didn't have any cooldown, but when it ran out of ammo it reloaded very fast (though Linn was helpless during the reload).
 * In the Battlefield series, there are mounted and man-portable machine guns. The previous has infinite ammo and the latter has limited ammo to force an occasional reload. They have effectively infinite reloads since the support class has the ability to supply ammunition.
 * The man-portable machine guns still overheat when too trigger happy.
 * In Call of Juarez, there are rusty weapons and normal weapons: the former overheat if you fire them too often and after you fire enough times, the latter only do the last part. Once a weapon overheats, however, it's no longer usable.
 * Sometimes it overheats, sometimes it just catastrophically fails, like the barrel rupturing or the cylinder exploding. Also, any normal gun will become rusty and eventually fail the more you fire it.
 * The horse-riding Sprint Meter in also inverted to function this way: in one (awesome) chase scene, it can be helpful to switch horses because the one you start with will tire.
 * In Gears of War, the mounted and man-portable machine guns will overheat and require you to "vent" it by using the Reload button. The game doesn't bother telling you that you can do this.
 * In the third Sly Cooper game, you drive a machine-gun-mounted gondola in a few missions. Using the machine gun too much will stop you from using it.
 * Mounted guns in Far Cry 2 will overheat if fired for too long; however, the portable version of the SAW light machine gun will never overheat, instead requiring reloads and having ridiculous muzzle climb.
 * In FEAR 2 the player is at one point given control of an automatic mounted grenade launcher, which will overheat if fired for too long. Oddly, though, if the player taps the fire button instead of holding it, the heat gauge will never increase.
 * The power armor machine guns also overheat after continuous firing and can be seen glowing in thermal vision.
 * This is how Dwarven Technologist Janos' Mana Meter is explained in Mage Knight: Apocalypse. He starts with zero heat, gains heat whenever he uses a skill, and when heat reaches 100, he must wait or use a 'coolant' potion.
 * Similarly, in Freedroid RPG, Tux heats up from casting spells (actually computer programs) and will blow up if he gets too hot.
 * Mounted guns in Killzone 2 overheat, with the meter being the visible top surface of the barrel, which goes from dull silver to bright red.
 * Machine guns in Crysis can overheat, and the ice-shard firing MOAC gun also works this way.
 * Happens in Resident Evil 5 when you continuously firing the Humvee machine gun for too long.
 * Your entire mech can have this problem in Armored Core 3. It was quite the Scrappy Mechanic.
 * In Robotech Battlecry, your Veritech's machine gun has infinite ammunition, but overheats after a few seconds. The Battloid's sniper mode lets you fire a Charged Attack that does more damage but instantly overheats the gun.
 * A core mechanic of the Amiga game Walker. Your Humongous Mecha is armed with twin guns that overheat if you fire them for too long, then they shut down until cool enough again. You don't really want this to happen when a wave of enemies is bearing down on you.
 * Warhawks have unlimited machine gun ammo. But their guns will overheat and temporarily jam after only a few seconds of continuous fire.
 * The Suffering 2 featured sections with vehicle mounted guns that would overheat. These weren't used for regular fights, only when the game was throwing wave after wave of enemies at you.
 * The first Soldner X game discourages constant fire by having your weapons overheat after prolonged firing.
 * Grand Chase does this with Mari's Gun Slinger job. The "heat gauge" fills up each round fired and will start to drain out if you stop shooting. If the gauge fills up all they full, the gun doesn't fire at all for a short time, leaving you with an attack that does nothing. However, it does not disable your MP Attacks at all, but only one of those uses the gun anyhow.
 * Brink has the 'ordinary guns need reloading, wall-mounted machineguns overheat' variant.
 * In Guilty Gear XX #Reload, Robo-Ky's tension meter is replaced with a unique power gauge and heat gauge. Specific moves increase his heat gauge, and if it maxes out he explodes, causing damage and knockdown to himself. However, his forward+hard slash command vents the heat in a cloud of steam, and it becomes more damaging the closer the heat gauge is to maximum. It's possible to chain together multiple vents before the gauge empties and the attack becomes ineffective again, though typically only one vent is necessary to bring Robo-Ky's heat back to safe levels.
 * In the Metroid Prime series, if you fire your Power Beam rapidly for an extended period it overheats and steam flows out of your gun. It doesn't affect your ability to fire and is purely cosmetic, however.
 * Happens in Persona 3 to Aigis herself after being in Orgia Mode for a full three turns.
 * In the Boktai series, your Gun Del Sol will overheat if you stay in intense sunlight for too long, causing it to jam temporarily, and take a short while in the shade (in-game or in real life) to cool down and allow it to fire again. Doing it this way prevents the player from regenerating their solar gun's energy near-instantly, and dissuades them from staying outside in intense sunlight for long periods, since the games use an UV sensor.
 * Call of Duty 4: Modern Warfare has the variant where mounted M249's, miniguns, and the Mk 19 have infinite ammo but can overheat, while the man-portable version of the former does not overheat but has limited ammo. Other games in the series, like World at War, have a variant where you can actually carry around mounted machine guns like the MG42 and mount them on their bipod yourself, but they still have limited ammo when mounted, and in some games in the series will overheat when fired like that anyway.
 * Deus Ex Human Revolution: the Heavy rifle (which would be more accurately called a light machine gun) overheats if you fire it for too long. A mod specific to that weapon is an enhanced cooling system that slows this down.
 * In Evolva, you have unlimited ammo for your attacks once you get them, but you must wait for them to charge again if you use them for too much time.
 * Team Fortress 2: the Dr. Grordbort weapons are overheating-type weapons in all but name. They have unlimited ammo, but must still be "reloaded" after four shots (five for the Cow Mangler).

Tabletop RPG

 * Traveller Classic. In Book 4 Mercenary, several rapid firing weapons (such as machine guns) would overheat and jam if you fired them too often, requiring repair.
 * In Battle Tech, heat is an important balancing factor. BattleMechs are environmentally sealed, powered by fusion engines and artificial muscles that aren't exactly 100% efficient, and often bristling with energy, ballistic, and/or missile weapons; virtually everything they do starting with simple movement will cause heat to build up, which needs to be funneled out of the 'Mech via dedicated 'heat sinks'. Build up heat faster than those can handle, and your 'Mech will slow down and the accuracy of its weapons fire will suffer until they have caught up again. At sufficiently high levels it may even automatically shut down and/or see explosive ammo start to cook off.
 * Many, many R&D megaweapons in Paranoia. They also tend to explode regularly.
 * Some weapons in Warhammer 40000 have a special rule called "Gets Hot!"; each time they're fired they have a 1 in 6 chance of "overheating" and injuring the operator. Most weapons with this rule are handheld plasma weapons, which harness energy equivalent to that of a star with technology the engineers have lost the blueprints to.
 * They're totally worth it, though.
 * GURPS High Tech naturally has detailed rules for overheating of automatic weapons, including barrel swaps, heating management by burst firing, and the possibility of spectacular malfunctions. GURPS Ultra Tech has optional overheating rules for energy weapons.

Real Life

 * Overheating weapons will reach a point at which they are incapable of firing- Particularly seen in light and heavy machine guns, which fire large volumes of rounds at a time (the typical belt size is 200 rounds). There are two reasons for this: First, steel expands when it gets sufficiently hot, causing stoppages (ie 'jamming') as the round travels through the bore (which is now too small for it to pass through). The other is that, since the barrel has a substantial weight, when it reaches higher temperatures it will in fact begin to bend, causing similar stoppages. Firing a gun to the point that it is severely overheated will eventually destroy the barrel in several ways. To prevent this, machine gunners carry spare barrels which they switch out after a certain number of rounds (or in a battle situation, 'whenever you have a chance'), allowing one barrel to cool while the other is in use.
 * That's the theory, anyway. When the barrels for a given machine gun are returned to an armorer, it's often found that one is a lot more worn than the other(s), indicating the gunner did not swap them often enough.
 * The U.S. Navy is attempting to design a functional railgun, and one the biggest issues they need to overcome is that the heat generated from firing warps the rails which severely limits the functional life of the weapon.
 * This is also a major limiter for hand-held laser weaponry... modern lithium batteries, capacitors, optics and indeed laser devices themselves are quite capable of delivering enough punch to be dangerous but at such a slow fire rate as to be useful only for research. Fire them fast enough to cause enough damage to compete with projectiles and you'll need a portable water cooling and chilling system far more bulky than any heavy machine gun. For now...
 * The modern desktop computer processor (be it a CPU or a higher-end GPU) creates enough waste heat to destroy itself in seconds if not properly cooled. A graphics card with a damaged or non-functional cooling system can easily reach over 100 degrees Celcius (hot enough to boil water) when under any kind of heavy processing load.