Editing Open bolt (section)

==Disadvantages==
Firstly, the bolt retention mechanism may fail, resulting in a spontaneous discharge (i.e., without prior trigger input), with potentially dangerous consequences. Some simple submachine gun designs, such as the [[Sten]], can discharge spontaneously when dropped onto a hard surface – even when uncocked – as the collision can jolt the bolt backward far enough that on returning it will pick up a round from the magazine, chamber it and fire it; the risk is intrinsic to hand-held open-bolt guns unless safety features are included in the design.

Another shortcoming of the open-bolt principle is that there is a brief delay between the trigger-pull and the firing of the cartridge because the (rather [[inertia|inert]]) bolt has to move forward a significant distance between the two events. Since after the first shot an open-bolt firearm operates effectively indistinguishably from a closed-bolt firearm, this latency problem is generally less of a concern in full automatic fire and mostly applies to semi-automatic mode. The issue was most problematic in the use of forward-firing open-bolt machine guns and autocannons in ([[tractor configuration]] single-engine) fighters during the piston engine era. Given the highly dynamic nature of aerial combat, the aforementioned intrinsic firing delay of open-bolt guns is particularly undesirable. The inertia and latency inherent to the open bolt design negatively affects predictability and control and makes fitting open-bolt designs with [[synchronization gear]] to fire through the propeller blades difficult and often requiring extensive modification (but not impossible).<ref>{{cite book |last=Woodman |first=Harry |date=1989|title=Early aircraft armament; the aeroplane and the gun up to 1918 |publisher=Smithsonian |pages=176–177|isbn=0853689903}}</ref><ref>{{Cite web|url=https://www.quarryhs.co.uk/Synchro.pdf|title=Synchronisation systems|archive-url=https://web.archive.org/web/20220103100812/https://www.quarryhs.co.uk/Synchro.pdf |archive-date=2022-01-03 }}</ref>

Furthermore, with unlocked [[Blowback_(firearms)#Simple_blowback|simple blowback]] action designs, calibers over [[9×19mm Parabellum]] become increasingly less practical because of the need for correspondingly heavier bolts as the chamber pressure increases. In simple blowback open-bolt designs, even in such relatively low-power calibers, the movement of the heavy bolt mass within the gun negatively affects aim and accuracy in two ways:

# In sustained automatic fire, it is difficult to keep the gun on target;
# In semi-automatic fire, or at the beginning of each automatic burst, the "latency problem" described above is exacerbated (due to the greater inertia of the heavier bolt).

While the latency is unavoidable with the open-bolt design, more sophisticated [[delayed-blowback]] open-bolt designs do allow for use of a lighter bolt, thus reducing the gap in performance between open and closed bolt types. However, these designs are uncommon due to economics and complexity.

Lastly, unless an ejection port cover is used, breech and action internals' exposure to the elements renders open-bolt designs universally vulnerable to contamination with dirt and dust through the open ejection port. Some versions of the open-bolt [[M3 submachine gun]] utilize a hinged sheet metal ejection port cover that doubles as a safety; when closed, it both covers the ejection port and blocks the bolt from closing. When ready to fire, the user simply flips the cover down, opening the ejection port and unblocking the bolt.