I have a question about powered armor as it is often used.

The issue is that of hand or arm mounted weapons. These are extremely common with suits like Iron Man or Bobbie Draper in The Expanse. How could this be practically justified?

  • 2
    $\begingroup$ one question per post, please $\endgroup$
    – L.Dutch
    Commented Apr 4, 2022 at 9:57
  • $\begingroup$ I removed the second question of your post to prevent the question from getting closed. Feel free to ask the second question separately. $\endgroup$
    – Philipp
    Commented Apr 4, 2022 at 9:58
  • $\begingroup$ Not sure if this is that realistic (a lot of it depends how futuristic your tech is) but I think the concept of arm-mounted weapons being built into the arm itself (like a cyborg) is cool. Otherwise, a wrist-mounted rocket or something is just going to be bulky and take up space compared to a handheld weapon. $\endgroup$
    – Mark Price
    Commented Apr 4, 2022 at 10:00
  • $\begingroup$ Philipp covered most of the good points below, but also consider the arm-mounted weapon as a backup weapon. That is, the one you use after you lose your main (hand-held) weapon. $\endgroup$
    – FuzzyChef
    Commented Apr 4, 2022 at 23:06

4 Answers 4


A gun mounted to the armor has several advantages:

  • When the weapon is integrated into their armor, then the soldier can not accidentally drop it. When the soldier gets thrown around by an explosion, engaged in melee combat or falls off a vehicle, then they might lose a handheld weapon. They would then be unarmed until they found it and picked it up again. These are valuable seconds which could make a difference between life and death.
  • They leave the soldiers hands free. When the soldier wants to grab something or use some equipment, then they don't need to holster their weapon first. This can again save valuable seconds in the heat of battle. They can even hold something in their hand while using their weapon. Like a hand scanner showing them where their enemies are. Or even a second weapon.

But it also has disadvantages:

  • It's probably difficult to aim without the assistance of the armor targeting systems. When the armor malfunctions, then it might not even be possible to fire it at all. So their combat effectiveness is tied to the reliability of the armor.

  • It's harder to replace a damaged arm-mounted weapon in the heat of battle. When a handheld weapon breaks, the soldier can just discard it and pick another one up from the ground. Even if it's one of the enemy. A weapon integrated into their armor might require a lot more work to remove and attach. And even if you give the guns a convenient quick-attach system: A replacement weapon you find on the battlefield might not be compatible with your armor.

  • When it's a particularly large gun, then its bulk might get in the way in close-quarter situations. A handheld weapon could just be holstered.

  • It makes it difficult to follow proper gun safety protocols. Rule #1 of gun safety is: "always point the muzzle in a safe direction"*. When the gun is attached to the soldiers arm, then that rule can be difficult to follow. Sure, the armor could implement all kinds of safety protocols to prevent accidental discharge. But any safety measure bears the risk of preventing the gun from firing when it should. So you can't go overboard with safety measures without hindering the soldiers effectiveness. Oh, and another common gun safety rule is: "do not rely on your gun's safety".

    This could perhaps be solved with a pop-out-and-unfold mechanic which hides the gun inside of the armor until the soldier wants to use it. Which admittedly could look pretty cool on a screen, but could raise further questions of practicality, reliability and how the mechanics actually work.

* or rule #2, depending on whose rules you follow. But I could not find a list of gun safety rules which didn't include this point pretty close to the top


Cannot be stolen

The weapon is on the arm because it makes the weapon easier to aim. Face or leg mounted weapons have a smaller range of motion and point in the wrong direction.

Of course all that means is the arm is the best way to AIM. The arm might not contain the weapon itself. It might just contain a guidance laser for a turret attached to the shoulder example. We tried that a few times but the more complex system was slower and known to malfunction when the baddies were shooting at us.

The alternative is a separate weapon. For example a jumbo rifle that the power armor holds like a normal rifle. This is more accurate since you don't need to retrain the user. They already know how to use a rifle accurately.

The downside is the jumbo rifle can be stolen. However the weapons attached to the suit are safe, unless the suit itself is defeated in battle. This is hard to do.



Like an officer's toolbelt or a soldier's chest rig, an arm mounted weapon is just another place you can store a specific-purpose weapon without really getting in the way (provided that the armor would support the weight of the weapon so you wouldn't have a hard time balancing). Let's say you carry a rifle but might need some kind of breacher-rocket. Boom, arm cannon.

fast access

they are a way to store additional equipment in an area on you that's easy and fast to access. A soldier keeps a grenade in a pouch or strap on the chest so that he can quickly reach it, if need be, and we keep guns in holsters so we can quickly access them, instead of having to dig through a backpack. The same point could be made with an arm cannon. It's a quick weapon/tool to be used, just in case.


The soldier you are facing is bristling with weapons. He even has a gun on his arm, thats some pretty advanced armor, this is a deadly adversary.


Putting the weapon along the arm means a lower moment of inertia and thus it can be brought to a specific bearing faster (given a fixed amount of actuator power) than the same weapon held in the hand. Assuming sufficiently good targeting systems this means that in a fair battle the guy with the arm-mount weapons always wins. (Note that in practice many encounters will not be fair, the real world effect is an advantage to the arm-mount weapons, not total superiority.)


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