The world where the question spans over a 100 years between 1945 and 2045, the story beginning just at the end of WWII, and proceeding in such a way that never saw the end of the Cold War all the way to 2045 and is centred around it. Many spy movies feature "unrealistic" cool gadgets, and while designing the world, I suddenly came up with this silly idea - an inner mouth mounted small-calibre (say, .22) pistol that could be activated by some form of tongue or tooth movement, firing a bullet from the agent's open mouth. There are a lot of safety hazards right off the bat, of course, but what interests me the most is whether such a weapon could

  • be designed to fit into an average adult man's mouth cavity
  • be shot without or with minimal damage to the operator

If such a weapon is possible, what is the earliest year it could theoretically be invented as a part of "weapons on steroids" general research of the agency?

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    $\begingroup$ Welcome to WorldBuilding Ivan! That is a great first question. Looking forward to the answers to this one and your future contributions to the site. Have fun! $\endgroup$
    – Secespitus
    Jul 3, 2018 at 14:37
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    $\begingroup$ This reminds me uncomfortably of a certain scene from Akame ga Kill. $\endgroup$
    – F1Krazy
    Jul 3, 2018 at 14:54
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    $\begingroup$ At the restaurant across the street, waiting for the Target to appear: "What can I get you?" "mmmf mmmh mmmd mmmf ah mmmh mmmmf. Ghz." $\endgroup$
    – user535733
    Jul 3, 2018 at 15:04
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    $\begingroup$ IvanTalanov You can find the scene @F1Krazy was referring to here --- WARNING: Much violence!! --- For more information about the Anime you can look here. The character's wiki only states that she can shoot bullets from a gun installed in her mouth though, so you won't get much information about how this could be done. But if you are just looking for unrealistic rule of cool guns this might give you some inspiration. $\endgroup$
    – Secespitus
    Jul 3, 2018 at 16:52
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    $\begingroup$ Blowpipes can be quite effective, with the right projectile - e.g. containing anaesthetic or nerve agent according to the lethality required. Technology level? Eccentric Victorian explorer returning from the Amazon rainforest. $\endgroup$ Jul 4, 2018 at 13:28

9 Answers 9


I love wacky questions!

OK, we need a removable object or our hapless test subject will have trouble eating and it must be made of surgical stainless steel or it'll start rusting very quickly. Stainless steel was invented in the early 1900s, so that's not an inhibitor.

Bolting things onto the human body is a bit more complex. Your first rod to help a broken bone was about the WWI time period but it didn't advance quickly. Bolts were first used around the WWII period, so it's plausible — unless your happy with the entire steampunk motif, in which case it's mandatory.

So, let's say the bottom end of our technology is the 1950s or early 1960s. We're going to bolt a stainless steel infrastructure to the upper and lower jaw areas between tooth roots to hold what would most likely be a single-shot also stainless steel firing mechanism. Various hooks and latches will be used for removal, leaving the bridle-like infrastructure in place to swallow around. It's inefficient, difficult to aim, definitely 1970s James Bond in its pure silliness, but it's plausible.

I wouldn't activate it with my tongue, too much liklihood of blowing a hole through my own teeth. Activate it by opening the mouth wide. You'll feel the tension as you're opening your mouth to the correct width, and finally Click! Bang! And then...

The real problem

The real problem is recoil. The human arm is wonderful at absorbing linear energy. It's almost as if it were designed to punch people in the nose. Your neck on the other hand, was not designed to withstand a lot of lateral energy. Let's call it whiplash.

Now, a .22 calibre bullet doesn't produce a ton of energy compared to its larger siblings, but it's there.

The acceleration-deceleration forces which cause whiplash injury are sufficient to permanently disable you. Even in a low speed rear impact collision of 8 mph, your head moves roughly 18 inches, at a force as great as 7 G’s in less than a quarter of a second. The Discovery space shuttle is only built to withstand a maximum of 3 G’s. (Source)

7G is 68.6 m/s2. In a quarter of a second that's about 17.15 m/s. A .22 bullet has a muzzle velocity of around 914 m/s. The average adult head is 4.5Kg, the bullet is 2g, that's a ratio of 4.4e-4 so the head is going to move, what, about 41 cm/s1 for more-or-less that quarter second. That's a long way away from the 17.17m/s we need for a dibilitating injury. It'll be a pain, but our intrepid agent of evil will survive.

Which means your real, real problem is...

Accuracy. I can't think of anything less accurate than a mouth gun. This is point-blank wet work only unless you've been distracted by, well, her... Let's just hope you're sent to assassinate a lady.

1This is my favorite way to quickly estimate the transfer of energy between two objects. It's inaccurate, but good enough for government work.


There is an analogue of the weapon you describe, which I saw in a pattern room in a museum once.

It was a .22 cal assassination weapon, disguised as a lady's compact:

enter image description here

Traditional ladies compact

The barrel was concealed in the lower case, and the assassin moved close to the target, removed the compact from her purse, opened the compact (cocking the action) and aiming either through a crude "notch" sight in top of the mirror, or an aiming line on the mirror itself (can't quite remember). To any casual observer, the lady was just adjusting her makeup or "powdering her nose".

The compact was lined up with the target now, so closing the lid also fired the action.

Naturally the user needed to make an allowance for the fingers when holding and aiming the device, but if I remember correctly, the barrel extended far enough out the back you could palm the device and have the barrel protrude through your fingers.

So in terms of size, a small, flat cylinder containing the barrel and mechanism could be designed to fit inside the mouth, perhaps disguised as a dental appliance.

enter image description here

Who would have seen that coming?

The awkward part is the operator could not eat, drink or maybe even speak with such a device inside the mouth, which in of itself might arouse suspicion. As many others have noted, aiming and firing the device without self injury would also be difficult....

The only other way to have that effect would be to disguise the weapon in a man's pipe. Holding it in the mouth and aiming over the pipe bowl while "filling" the bowl with tobacco and then lighting it, you also have your hand to both steady the front of the weapon and make any final aiming adjustments. This also protects your teeth from being broken when the weapon fires, and as a bonus, the cloud of smoke coming from the pipe provides a very handy way of disguising the smoke and flash of the discharge of the weapon.

enter image description here

What noise? I didn't hear anything

So while an actual firearm concealed inside the mouth is probably impractical, there are workarounds if you are clever enough.

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    $\begingroup$ The thought of Günter Grass being a pipe-smoking secret agent assassin makes me smile. $\endgroup$ Jul 3, 2018 at 22:47
  • $\begingroup$ There was a lot more to that guy than most people realize....... $\endgroup$
    – Thucydides
    Jul 3, 2018 at 23:13
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    $\begingroup$ ... or a woman's pipe. $\endgroup$ Jul 4, 2018 at 8:59
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    $\begingroup$ @MartinBonner ... or a man's compact. $\endgroup$
    – Michael
    Jul 4, 2018 at 10:55
  • $\begingroup$ @Michael I know no men who use compacts, but I did know a pipe-smoking woman. $\endgroup$ Jul 4, 2018 at 11:58

Is the gun completely within the mouth, or can the end of the barrel stick out past the lips?

If the gun is completely within the mouth, you have two problems. First, you need to be worried about shooting your lips or possibly even your teeth. It could probably be mounted in such a way that it could not fire if the teeth were in the way, but I don't know if that could be done for your lips. They're pretty soft and would have difficulty toggling any safety mechanism. The second problem is combustion gases. These are very hot and very high pressure. They would not cause life-threatening injuries, but will almost certainly burn your tongue and the inside of your lips. They may also knock your front teeth out.

If the barrel of the gun sticks out of your mouth, you avoid these problems but have to deal with much higher recoil. Recoil is proportional to muzzle velocity, which is itself proportional to barrel length. Longer barrel means higher muzzle velocity which means more recoil. The recoil calculations in the answers above don't take into account the fact that your head is connected to a ~55kg body. Their estimates are high, but exactly how high depends greatly on how exactly the gun is mounted and whether the shooter can support his head in some other way. The gun could have springs at the back which would reduce felt recoil. The shooter could put his hands on the back of his head and push his head forward. This would mean his arms and shoulders would take some of the recoil instead of his neck.

Either way it would be horrible on your ears. Anyone who has ever fired one of those little derringers knows they are much louder than you expect. I can't imagine how loud it would be inside your mouth. We're probably looking at permanent hearing loss from a single shot. Further, I don't believe ear plugs will help because they block sound from outside of your head, not from inside your head.


What you describe is basically a custom .22 derringer once you have brass cartridge ammunition you could mouth mount such a weapon. Without water proof cartridges the moist nature of the mouth would be a major issue. My understanding is that such weapons have almost no recoil or chamber heating on firing so the biggest injury risks are going to be in terms of burns from the GSR and the possibility of self-inflicted bullet wounds.


be designed to fit into an average adult man's mouth cavity be shot without or with minimum damage to the operator

Yes to both. You would need a special setup to keep the bullet dry (probably seal everything in rubber). Also, the gas discharge would need to be sent forward, increasing the recoil (you'd have three barrels going out - a central one for the gun and two for the exhaust gases).

I have read that weight goes "(1.3 to 3.9 g), and velocities vary from 575 to 1,750 ft/s (175 to 533 m/s)" (Wikipedia).

Assuming 300 m/s and 2 grams, the barrel could be say 5 cm (we would need a very powerful explosive). This gives an acceleration of 0 to 300 m/s in a space of 5 cm, and since v = SQRT(2*a*s) it must be 300 = SQRT(2*a*0.05) or a = 900000 m/s^2 (ninety thousand G's).

An average human head weighs say 5 kg or 5000 grams. The recoil equation says that m1a1 = m2a2, so 2*90000 = 5000*a2 and a2, the acceleration of the head, would be around 36 gravities, which would be the equivalent of hitting a not-so-soft mat from about a half meter of height.

You'd almost certainly get severe whiplash, and possibly also a concussion, but if you're shooting a one-shot gun from your mouth you're probably way past worrying for that.

You could decrease the muzzle speed of the bullet (but I'm a total ignoramus about weapons; I only know that if you reduce the muzzle speed by a factor of four, acceleration halves). Also adding a considerable weight to the gun would help, or mounting it on a spring release with dampers (the gun is 5 cm long when in the mouth, then pops out for about as much, becoming double the length; that reduces the recoil by half).

You'd probably also need a fourth barrel with a laser pointer to aid in aiming the thing.

(A similar setup)

  • $\begingroup$ The bullet is waterproof, so is the cartridge. All that needs to be done is to seal where the bullet meets the cartridge. This is already a thing that is commonly done, especially with ammunition intended for rough duty (military, for example). $\endgroup$ Jul 3, 2018 at 20:56
  • $\begingroup$ Why would you need extra barrels to vent gasses? There's no advantage to that if you don't have a gas-operated mechanism. $\endgroup$
    – Fax
    Jul 3, 2018 at 22:56
  • $\begingroup$ @Fax not actually "barrels", but rather venting outlets. Unless the mechanism is built in such a way that there are no gases escaping except from the muzzle, which would be outside the mouth anyway. $\endgroup$
    – LSerni
    Jul 3, 2018 at 22:59


A gun is a chamber for containing and directing the force of an explosion. Purists will argue that gunpowder doesn't explode, it burns and expands rapidly, but i'll argue back that the recoil from a gun is sufficient that for this discussion it qualifies as an explosion.

The brain is essentially two big blobs of tissue with approximately the consistency of butter floating in water, housed inside a rough boney box with lots of sharp edges, that it is partially attached to.

On firing, a shockwave (what we hear as a "bang") will be propagated through the bone, the cerebro-spinal fluid, and the brain itself. The vibration in the bone will bruise the lower surfaces of the brain where the skull and brain are in direct contact, resulting in immediate loss of the sense of smell, and possible bruising of the optic nerve.

The delicate nerves in the inner ear will be bruised, resulting in loss of equilibrium and hearing. It is possible that calcium deposits that often form in the inner ear can be dislodged and cause further issues with equilibrium.

Another instant effect of the shockwave on the brain will be the triggering of a seizure and secondary injuries. Warning: graphic content: https://www.dailymotion.com/video/x24x49b

The eyes, likewise, are essentially water filled bags of tissue. The shockwave will likely cause detached retina and bleeding inside the eyes themselves, resulting in instant and permanent degradation of vision and be probably blindness.

The operator would likely suffer long term effects as well. Alexithymia is the inability to process emotions, which renders the person incapable of recognizing or responding to normal social cues, impacts their ability to form new memories, or to prioritize.

All of the previous will probably be immaterial, though. Water is a much better conductor of energy than air, so the "bang" that you hear and find deafening will be much worse in the confines of the skull. Someone better at math than I am will need to do the computations, but I suspect that the shockwave going through the braincase would simply puree the brain, resulting in instant death.



The top answer is good, I just want to add some things:

  • You don't really want an explosion in your mouth (nor the gasses nor shell from the aftermath).
  • What about a tiny gas canister that uses pressurized air? Air powered guns are already a common thing—they are quieter than a firearm, and the wild inaccuracy of mouth-aiming means you'll be close to the target anyway, so you don't need to worry about power.
  • Recoil might be hazardous, but that could be part of how it works. "Brace your head against something (e.g. pressed against a wall), or prepare to sustain injury". Sometimes limitations make the world interesting, you don't need a perfect weapon.

Update—some concerns:

  • There's nothing for the weapon to hold on to, the mouth is pretty squishy.
  • Eating food would be difficult and gross, food would get stuck on the weapon and rot in your mouth (but maybe that's part of the story, the killer with the horrible breath).
  • Speaking would be difficult, try putting something in your mouth and talking.

The only thing I can think of is...

Removing the upper palate, and storing the weapon in the nasal cavity. Then the weapon becomes an artificial roof of your mouth, you can speak, eat, etc normally, and with some special movement you can lower the weapon into your mouth and fire it. The cost here is you can no longer smell/breathe in through your nose.

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    $\begingroup$ If your head is braced, then the energy of recoil will go to compressing tissues instead of causing the head to move. Whether or not that is better depends upon whether those tissues can be safely compressed. $\endgroup$ Jul 4, 2018 at 1:32

It should be doable during the entire range of years you're looking at. You'd have to play with the caliber and probably use a weak, subsonic round.. but it's probably doable using WW2 technology.

Being able to be shot with minimal damage to the operator is tricky. Not so much the technical part of making the gun itself, but you are going to have to use it at point blank range, aren't going to be able to hide the fact that you did it and are likely to be a bit rattled after you fire it. And it's going to be such an inaccurate and weak round that you're probably going to fail unless your target is a few feet away from you.

Unless you're going for an Austin Powers level of silliness, perhaps you'd be better served going for a mouth mounted poison dart launcher. That would be small and silent enough that you'd actually have a decent chance of surviving using it.

  • $\begingroup$ Well yes, but that would be called a blowgun :-) $\endgroup$
    – LSerni
    Jul 3, 2018 at 22:36
  • $\begingroup$ Kissing the subject would aim it fairly well and let you hold up the body so it does not collapse suddenly. $\endgroup$
    – KalleMP
    Sep 6, 2018 at 7:53

If instead of firing a bullet you launched a small rocket, you could avoid the majority of the recoil and outgassing. A bullet-sized rocket with its own propellant could be launched using either a small amount of gunpowder or even compressed air, using just enough force to get it out of your mouth (and far enough from your face) where the main propellent would ignite and do the majority of the acceleration away from your body.

There was a series of firearms developed in the 60s that used this principle, called the Gyrojet (see wikipedia: https://en.wikipedia.org/wiki/Gyrojet). There was a derringer version you could adapt to fit inside a mouth, using similar principles for mounting & operation from the previous answers.

Aiming would still be a problem as with a regular bullet, and the rocket itself is not as accurate, but damage at longer range is increased (assuming you hit the target).

Recoil and gasses would be much reduced, and the launcher itself would be much smaller/simpler as you don't have the same barrel stresses. The majority of the size and complexity is in the round itself.

It would also be stealthier since less recoil and gassing means you can recover more quickly after firing. The sound would also be different, less an immediate crack of the initial firing as with a traditional bullet, and more of a hissing as the round accelerates.

  • $\begingroup$ That sounds even more crazy than my original idea, and I like that, especially since this kind of weapon will be less harmful to the user. I might even implement this variant in the final work alongside, if not instead the original. $\endgroup$
    – Ivan T.
    Jul 4, 2018 at 10:22
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    $\begingroup$ I immediately thought of the Gyrojet, too. One drawback to the design was that the rockets would take much longer to get up to speed than a regular bullet, which is at max velocity as it leaves the barrel. This makes them ineffective closer than some minimum distance, which makes them less useful for close up assassinations in your plot. Here's a good video with details: youtube.com/watch?v=98c2t_uK5Uo $\endgroup$
    – Beejamin
    Jul 5, 2018 at 7:27

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