Every Firearm Is Open Bolt

Semi-automatic and automatic firearms have two main methods of operation: Open Bolt and Closed Bolt. In an open bolt system, the bolt is back when inactive and goes forward to fire then driven back to its initial position by the firing. In a closed bolt system the bolt is driven backwards, then forward. Most modern firearms, with the exception of some (sub)machine guns, are closed bolt or a hybrid as are nearly all civilian legal firearms.

While these systems have a large host of differences in reliability, accuracy, fire rate, fire modes, compatibility with interrupter gears, and legal regulations (making an open bolt firearm full auto proof is extremely difficult) one of the most obvious differences between the two for an end user is the ability for closed bolt firearms to hold an extra round in the chamber, in addition to what is stored in the magazine. This extra cartridge persists across magazine changes and is referred to as "+1" when dealing with capacity (30+1). When reloading with a round left in the chamber the current magazine only needs to be ejected and replaced, with none of the other controls needing to be touched. Ignorance of the +1 has lead to the injury and death of many people that fail to obey the four rules and didn't realize it can fire with the magazine removed, especially among poorly trained police and untrained civilians. This has led to laws mandating loaded chamber indicators, magazine disconnect safeties and ugly white "caution-capable of firing with magazine removed" markings on firearms.

In most video games however, even otherwise "realistic" ones, every firearm behaves as though it were open bolt in regards to chambered rounds. Your maximum capacity will always be the magazine capacity and the reload animation will always feature characters manually cambering a new round, even when not reloading from empty. The only common exceptions are firearms that are actually open bolt, and those that do not feed from detachable magazines including shotguns (both pump action and break action, but not magazine fed), belt feds, grenade launchers, single shot firearms and revolvers, which don't have to deal with +1 in the first place or in the case of pump action shotguns have a separate problem of being given the +1 capacity without actually having to chamber a round.

Overlaps with Right-Handed Left-Handed Guns and One Bullet Clips. Often combined with Dramatic Gun Cock to use the same error twice but in reverse. For every gun having the safety problems typical of simpler open bolt designs see Reliably Unreliable Guns.

Video Games

 * Metal Gear
 * Metal Gear Solid 3: Snake Eater indulges in this trope for most weapons. In a rather amusing Epic Fail sequence early on, Ocelot attempts to avert this by circumventing how this does NOT apply to his Makarov by surreptitiously adding a round to the gun as he turns to fire at Snake, and only succeeds in rendering his gun useless because he didn't know what he was doing and got his ass handed to him for his trouble.
 * Metal Gear Solid 5: Done partially to keep gameplay fun, and can be partially justified by the ingame weapons modification mechanics that allow for gun modding.
 * Fallout
 * Fallout: New Vegas uses this trope quite a bit, even invoking it with some of the shotguns.
 * Fallout 4 allows for the modification of some guns to use certain loadout schemes, thus applying this trope at the player's preference.
 * Rainbow Six series beginning with Vegas. This is odd as Vegas otherwise marked a move away from realism.
 * Inverted by Rainbow Six: Siege where open bolt firearms have +1 capacity like closed bolt ones.
 * Crysis 2
 * Metro 2033 plays this straight, however its Updated Rerelease Metro Redux fixes it.
 * While earlier Battlefield games feature this problem, the third game onward avoids it.
 * Far Cry 4 includes this... except for the pump shotgun, which has the correct capacity and is +1ed correctly when reloading as the player character will load one, pump then load the rest. Far Cry 5 continues this, though changes the animation to inserting the shell directly into the chamber to make what is going on clearer to people who have never touched a firearm. This detail is very strangely juxtaposed next to wildly incorrect models (some of which actually get worse as the series goes along), descriptions (Some as blatant as claiming a 1924 gun hasn't changed since World War I), handling and placement for everything else.