I have a race in my world that in most respects is comparable to a human, perhaps not in form but certainly in function.

One of the key differences between humans and this species is a lack of opposable thumbs.

  • This species still has five fingers.
  • The fifth, instead of being a thumb is essentially an extra pinky where the thumb would be, this changes the wrist bones and all that.
  • Their fingers are slightly longer and slightly stronger
  • Their manual dexterity is slightly lower than a human, meaning precision is a bit lower.

As in the title I am particularly concerned with how this would impact the development of firearms. For the sake of this question assume all other aspects of using a firearm are functionally the same as a human. (aiming for example)

Firearm Requirements:

  • Must be for personal use, meaning only one person needed
  • Include design considerations for both pistols and rifles (both single and burst/auto)
  • How will it be held
  • How will the trigger be situated
  • Ensure reload is effectively easy
  • The weapons should stay as similar to modern ballistic firearms as possible
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    $\begingroup$ how do they hold a hammer, that is how they will have to hold a firearm. $\endgroup$
    – John
    Commented Jun 23, 2017 at 14:31
  • $\begingroup$ There are people that have no thumbs. Maybe you will find something if you do research in that direction $\endgroup$
    – Raditz_35
    Commented Jun 23, 2017 at 14:37
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    $\begingroup$ If a species developed without thumbs, it would change everything, even if they are the same as humans in most aspects, their tech would be vastly different to cope with the obvious deficit of having no thumbs. $\endgroup$
    – Hyfnae
    Commented Jun 23, 2017 at 14:43
  • 1
    $\begingroup$ @Mołot Thats the question... $\endgroup$
    – James
    Commented Jun 23, 2017 at 14:50
  • 3
    $\begingroup$ @James question as stated asks for firearms design and assumes tools usage good enough to craft firearms. $\endgroup$
    – Mołot
    Commented Jun 23, 2017 at 14:52

6 Answers 6


There won't be any diagonal gun grips

There are six main motions that the human hand can make:

  • cylindrical grasp
  • tip grasp (between finger tip and thumb tip)
  • hook grip
  • palmar (between pad of finger and pad of thumb)
  • spherical grasp
  • lateral grasp (pad of thumb and side of pointer finger)

Grip Types

Of these six, only one can be done for sure without a thumb. The others are either impossible or very clumsy.

Because the pistol grip typically used by humans on our firearms requires a thumb, that grip style won't work for these five-fingered-no-thumbs people. Since the cylindrical grip still maintains a great degree of power and control over the hook grasp, we'll design a firearm grip around that motion.

Because they no longer have a thumb to brace against the recoil of the weapon, the recoil will need to go somewhere else. It can't go into the fingers because the grip is moving in the weakest direction for the fingers to grasp (ie, the grip is moving back towards the wrist, away from the fingers). The wrist and forearm seem the best place for me. If the barrel of the firearm is placed co-linear with the axis of the firearm, accuracy can be preserved as well as recoil force put into larger/stronger body structures.

Something like this.

I'm sure that some clever machinist is going to come up with a different, better, more efficient firearm than I just did. I don't see how you would use any other finger for the trigger other than the "thumb" or the pinky since all the other fingers would benefit from being squeezed together.

There's plenty of space to innovate. This doesn't address in the least the problems with loading shells into the gun since humans use a pinch grip when loading rounds. These non-humans can only do pinching motions in a very clumsy way. I don't know how you could make reloading efficient given the inferior grips available to these creatures.

Rifles could easily dispense with the forearm brace and use a shoulder butt much like normal human rifles do. The above (and very crude) diagram shows a possible pistol sized weapon.

  • $\begingroup$ How would they, especially the second one, handle recoil? $\endgroup$
    – vsz
    Commented Jun 23, 2017 at 18:23
  • $\begingroup$ @vsz recoil is transfered by the collar into compression of the forearm tissues. It can't go into the hand since the fingers aren't strong enough to handle it. $\endgroup$
    – Green
    Commented Jun 23, 2017 at 18:25
  • $\begingroup$ Aren't tip, hook/snap, and palmar just special cases of cylindrical and spherical? $\endgroup$
    – jpmc26
    Commented Jun 24, 2017 at 4:24

Take a look at "old style" crossbows - trigger mechanism was a lever underneath the hand grip, simply squeeze. May be easier to do it with a thumb around the top of the stock, but with a longer palm having the heel on top and wrapping those longer fingers around should do just fine. For pistols check out the "squeeze action" Protector Palm Pistol - based on image not having a thumb shouldn't be an issue. Range and accuracy issues though...

Medieval style crossbow w/ lever trigger

Protector Palm Pistol


When life gives you lemons...

... in this case, don't make lemon grenades. Just make do and turn your fingers into thumbs.

For example, try gripping some sort of handle with your two middle fingers on the front (as normal), but your index and pinky fingers on the back (so the backs of the fingers are touching the handle). It feels weird, but it should work. Now, imagine you've been holding things like that your whole life. The human body would have adapted to make this grip easier for you; this fictional species should have the same adaptability. Similarly, gloves are great at improving grip, so maybe this species has specialized gloves they can wear that make this kind of grip even easier.

So I'm thinking you could make firearms pretty much the same as they do now. It seems like grips would have to be thinner, which means magazines will have to go in somewhere else (which they already do for most guns, I'm just saying pistols will look different). The trigger will have to be operated by the middle finger (gives a whole new meaning to flipping someone off). Other than that, I'm thinking things could stay the same.

I know this is kind of avoiding the premise, but I think opposable thumbs are so useful, that something similar to them has to be one of the first inventions of an intelligent species. If they can't get them through evolution, then they can get them through practice.

Anyway, here's a picture of what I'm describing: sketch of alien hands

  • 1
    $\begingroup$ I doubt that the recoil would be healthy for the angled fingers... $\endgroup$ Commented Jun 23, 2017 at 19:41
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    $\begingroup$ @cmaster it'd definitely be a problem for us, but I think it'd be fine if your hand was accustomed to it, and you held it right (keep the force between your fingers instead of on them). $\endgroup$ Commented Jun 23, 2017 at 19:49

something like a suitcase gun handle might work, or like the guitar gun from desperado. Both are terrible for aiming though, but on the other hand bulk would be less of an issue. With this recoil would also be more of a problem on large guns, something more like a normal rifle would be good for larger guns. Shoulder bracing will make even human long guns work fine.

the real issue is how do they build them without the ability to do precision grips.

enter image description here

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TDLR; Make it triggered by the shoulder, and loaded vertically from the front.

enter image description here

Using an electric mechanism on the shoulder, you avoid any typical trigger mechanism, and can use a basic electrical connection (similar to a flashlight), to trigger the firing pin. Other options may include mechanical firing mechanisms, but this may add weight to the weapon. Rotating the bullets by 90 degrees allow for a hand on the foregrip, and the other to be loading bullets, similar to a shotgun.

If you're worried about accidental discharge, you can add a hand trigger (a grip with a button on it to make a similar electrical connection), and hold the weapon without it depressed.

The advantages are continuous loading, allowing for a never ending stream of bullet, simply design, tactical/logistical ease, and universal usability (we could use this now if we wanted!).

Downsides as mentioned are accidental discharge, sniping inaccuracy, and general gun maintenence. The stock would most likely be hollowed out to make room for firig mechanism, but would require extra weight to allow for possibly multiple buttons, and the mechanism would not be as conducive to sniping due to the movement involved. The mechanism itself would be difficult to clean on the go, and any gun maintenance in general is difficult without thumbs to make pinching motions.

As for pistols, just add a stock (a lot of pistols have stocks as well). You could make it single shot and loaded directly onto the barrel, or expect that reloading would use multiple smaller magazines with a smaller barrel.

  • 2
    $\begingroup$ One anachronism involved in this is that (in the human development of firearms) the first firearms were developed over 600 years prior to the development of any dry cell batteries; wet cell batteries would be -- at the least -- impractical to integrate reliably into a gun. I think a mechanical firing mechanism that runs through the stock would make more sense from a developmental evolution perspective. $\endgroup$
    – Doktor J
    Commented Jun 23, 2017 at 19:42
  • $\begingroup$ You've missed an obvious and huge disadvantage. If you have to bump the gun with your shoulder to fire it, you can't shoot straight. You want the gun to be still while you fire it. $\endgroup$ Commented Jun 24, 2017 at 9:10
  • $\begingroup$ I would have hoped for a design that used engineering to overcome some of the limitations of the species physical traits. This design will only exacerbate them. One of the most important bits about accurate firing is to not be moving the gun or your body at all. Snipers are careful about even their breathing. This design would require both the gun and arms to be in motion (or the entire body). Combined with the reduced dexterity of this species the firing accuracy would be abominable. $\endgroup$
    – Caleb
    Commented Jun 24, 2017 at 14:43
  • $\begingroup$ @DavidRicherby Not necessarily. One of the most obvious mistakes people make when shooting (that leads to horrendous accuracy and bruising) is not holding the gun tight enough to their "shoulder". To increase the accuracy and decrease recoil, this design would actually help to eliminate common shooter mistakes and make them easier to fire more accurately. Although this design doesn't work as well for sniping, both automatic weaponry and shotgunning, both which are commonly seen as the most common utility weapons at a higher rate than snipers, would actually see a usage improvement. $\endgroup$
    – Anoplexian
    Commented Jun 26, 2017 at 14:27
  • $\begingroup$ @Anoplexian I'm certainly no expert but It seems to me that your proposed mechanism would make it worse, by making it impossible to securely seat the gun against your shoulder before firing. $\endgroup$ Commented Jun 26, 2017 at 16:48

Rat-like grip

Rats have surprisingly dextrous hands despite lacking opposable thumbs (or really anything resembling a thumb). Rats can grip objects by pressing them between their palm and fingers, or more often with a two-handed grip. (You can see this two-handed grip most easily if you watch a rat eat something small.)

Their guns would likely be designed to be gripped between two hands. Pulling a trigger just requires a free index finger.

For reloading, you'd have the magazine designed to comfortably fit between the fingers and palm, and not require much dexterity to put in, because one-handed grip is far less dextrous than two-handed. You'd probably also design the gun to be braced against the body while reloading, so you can maintain a one-handed hold on the gun.


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