Can I have a character make use of a handheld speargun in a postapocalyptic setting to shoot people and pull them back (or at least retain them) with the gun's cord?

I came across some criteria/problems that might influence how useful this weapon might be and hence how this question might be answered if someone has information on them:

  • A speargun can be powered using rubber bands or pneumatic propulsion but I haven't found any general information how strong either of those methods is. The weapon should have enough impact and range to go deep enough into/through human flesh to be able to pull the person back with the cord, being shot from some distance. I do know that there was an accident with a teenager being accidentally shot through the head with a speargun, but I don't know the distance of said shooter.

  • I also read that the recoil could be impossible to handle out of the water (which would make it completely useless), while in the first linked video this didn't seem to be much of a problem.

  • The whole story is set in a postapocalyptic world so spare parts and competent mechanics are rare... That being said it can be a deal-breaker if those gadgets get broken easily or the gas cartridge or the rubber band only last for a short time of use.
    The setting is the ruins of a present-day metropolis (not a wasteland) and there is some trade with recovered old-world-stuff going on so rich people could be able to get in possession of a well-preserved present-day weapon but finding spare parts for one particular model should prove very difficult. Also there is no industry going on to just produce weapons of the same effectiveness oneself.
  • I also noticed that the cord of spearguns looks pretty thin, maybe too weak to pull a human back or at least restrain him/her if used out of the weight-reducing water. The crank for the cord also looks very tiny but one could simply pull back the rope by hand in a pinch. If the original cord should prove too weak it could be replaced by something stronger, but this could make the missile too heavy to be effective. And the pull-back-function is the one benefit that sets that weapon apart from others.
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    $\begingroup$ One question per post please. Else it is overly broad. $\endgroup$ – L.Dutch - Reinstate Monica Aug 28 '19 at 16:57
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    $\begingroup$ We have a clear policy: one question per post. $\endgroup$ – L.Dutch - Reinstate Monica Aug 28 '19 at 17:05
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    $\begingroup$ Spearguns aren't all that powerful, really just a very weak crossbow. They're very much short-distance weapons. On land, you'd be much better off using something like an atlatl: waa.basketmakeratlatl.com/?page_id=177 $\endgroup$ – jamesqf Aug 28 '19 at 17:44
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    $\begingroup$ Don't know much about spearguns but I have seen a few old homemade ones that use inner tube rubber hacked from an old tire. In a post apocalyptic scenario, inner tubes are going to be a lot easier to scavenge than pneumatic parts. $\endgroup$ – Henry Taylor Aug 28 '19 at 18:10
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    $\begingroup$ @CeeMon you would have the same problem with any pneumatic system that will probably use perishable rubber seals to maintain their pressure. $\endgroup$ – Sarriesfan Aug 28 '19 at 18:35

It is an ineffective weapon for capturing slaves on many levels

Lack of Range:

When you launch an arrow, there is a lot of resistance from inertia, but once it's up to speed, there is very little drag to slow it down in atmosphere. This is why a bow and arrow can pierce a target from far away with little more energy than you would need to thrust the arrow into something at point blank. Once, you attach a cord to the arrow, it applies continuous and incrementally increasing resistance as it leaves the bow. The spool pulls back at the arrow, and the weight of the unraveling cord adds additional drag, the more it unravels. This very significantly decreases the effective range of the weapon to only a few meters before the missile is moving too slowly to sink it's barbs deep enough to catch flesh.

In water, attaching a rope to a harpoon this is less of a concern because the water already has such high resistance that you aren't expecting much range anyway, but in air, the difference is pretty extreme.

Unable to drag a live person:

Another consideration is that a cord strong enough to pull a live person back with is also going to be pretty heavy. A harpoon is designed to keep the fish you killed from sinking, it is not meant to pull back live prey. Most human sized fish can be pulled in with a thin, lightweight line rated for 20-50lb of resistance, but a full grown human running away at full speed will exert hundreds of pounds of pull between their mass and momentum snapping even the heaviest of fishing lines. In a world without modern industry, making your own line that can overcome a moving human's inertia light enough to be pulled by a harpoon is not going to be easy. It is also likely that a person's inneria will be more than enough to rip out the harpoon when you try to yank them back.

Slaves are worth more alive than dead:

While there are psychological advantages to keeping your slaves afraid to run away, the kind of wounds a barbed harpoon can do are so maiming, that even a shot to the leg or arm will likely make your victims bleed out and die pretty quickly. At this point, you are better off just ditching the rope and using the spear gun as a killing weapon for the better range.

===== Alternative Solution =====

Modify the spear gun to be a bolas launcher. Where a harpoon must impact at high speeds to pierce a target, a bolas can wrap around and capture a target at much lower speeds meaning that your drag-line will have less effect on the weapon's effective range. A bolas also becomes more secure the harder you pull against it, and does not kill your victim making it a better tool for actually capturing people.

While this does not have have the psychological advantages of harpoon gun, that does not mean it could not be made to be more inhumane. By binding your bolas balls with barbed wire or razor wire, you would not only improve your weapon's grip, but cause some very nasty lacerations as you drag them in. These laceractions would be very painful, visually disturbing, and cause scarring that would serve as a permanent reminder of what happens when you run, but the cuts would be mostly surface level meaning that your slave should be fit to resume his duties within a few days.

On a final note: Slavery is not about being cruel, it is about making money and offsetting risks. This is an important factor when trying to write a believable story about slavery. While many slaves did die as part of the American slave trade, it was almost never resulting from cruelty for cruelty sake. Slavers were businessmen. If they could transport 50 slaves and arrive with 50 slaves alive, or transport 200 slaves and arrive with 150 slaves alive, then they would measure the profit margins of each scenario and make their choices accordingly. The outcome was brutal, but that was not their goal, just a side-effect. Likewise, whatever tools and weapons your slavers use will be based on what is most profitable. Humaninely capturing a slave, then thoughtfully torturing him in such a manner that he remains fit to work hours later creates much more foreboding and feelings of powerlessness than seeing someone dragged in with a spear in his leg. It is powerlessness and not fear that controls people. Powerlessness is where the profits are.

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    $\begingroup$ Good points, especially the last ones. I'm definitively going to use bolas to equip at least one slaver. Maybe I'm thinking too much in scenes (the concept is for TV and Gaming and I picture the escapee being almost successfully out of reach before the antagonist grabs his weapon and the spear suddenly sticks out of the escapee's limb.) But my goal is to be realistic and not just do some fancy looking sh#t. $\endgroup$ – Cee Mon Aug 29 '19 at 20:39
  • $\begingroup$ Yes, slavery is a business and in a post apocalyptic world every workforce is desperately needed (which is also the reason that slavery has replaced death penalty in my world in most cases). On the other hand what kind of person devotes his life to capture and sell humans… and what kind of person is able to make it to the leader of a pack of freelance slavers (not just the captain of a slave ship, controlled by a British merchant company). I always imagined him as a predator. A passionate hunter to whom it means everything to always win and never let anyone escape. $\endgroup$ – Cee Mon Aug 29 '19 at 20:54
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    $\begingroup$ You are right that slave trade would attract sociopathic people. But, the ones that don't think about profits first would soon find themselves subservient to those with the money to hire more men and purchase better equipment. I think a cruel for cruelty sake villain can work as long as you don't try to pass him off as the biggest fish in the pond, but the technical limitations of a spear gun are going to make that particular scene unrealistic. $\endgroup$ – Nosajimiki - Reinstate Monica Aug 29 '19 at 21:25
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    $\begingroup$ For the Romans crucifying those slaves was not cruelty for cruelties sake it was a means to an end. Any other slave in the Empire would know the fate of those who opposed the will of Rome. Rioting is worse than just escaping it’s damaging Roman property, endangering the lives of Roman citizens and had to be put down. Ned Low lasted a brief 3 years as a pirate not so very long, and Amon Göth has the advantage of sitting within a system where he could perform his terrible atrocities. $\endgroup$ – Sarriesfan Aug 29 '19 at 22:29
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    $\begingroup$ Also, Amon Göth was not a slaver in the traditional since. Concentration camps were machinations for genocide: "the final solution". The fact that they performed forced labor at all was a cover for this real goal. If the concentration camps were required to pay the Gestapo for each Jewish worker, or had the option to sell their excess workers to other camps for more revenue, they would have been run very differently. $\endgroup$ – Nosajimiki - Reinstate Monica Aug 30 '19 at 13:54

My speargun is pneumatic. Manual strongly advises against using outside water because there is no resistance (from water) to keep its piston from harming itself. That can probably be addressed by having a spring on the end stroke.

Now, can it or its rubber band cousin work as dry land weapons?

Short version: YES.

Long version: their range/effectiveness primarily depend on providing them enough potential energy (air pressure, rubber bands). A ballista can be placed somewhere between a crossbow and a rubber speargun. The one in the picture below could work underwater:

Roman ballista (source: wikipedia)

If you replace the main tube in my pneumatic speargun with a nice steel pipe you scavenged somewhere (will need to polish the inside to protect the o-ring), you can probably increase its pressure a lot. There will be a point you will need to rethink how the piston seals it but there are enough examples out there of air pistols handling 1000psi or higher with rubber seals to build upon. By then you are redesigning the speargun, which you would in a survival situation if that is your only weapon and you have a source of parts. However, you would have to consider different settings for different applications: underwater you want the projectile to move slower than in air or it will not go very far (rifle bullets don't go very far under water because of their speed).

Air powered weapons can be designed to be quite effective; remember that the weapon Laws and Clark had the natives feared/respected the most was their Girandoni air rifle, which with its 20 round (fed from a tube) capacity before recharging and 150yd lethal range was possibly the first magazine-fed repetition rifle (as opposite to single shot) in service in North America. Your garden-variety compressed air spear gun or pump air rifle operate at much lesser pressures; modern materials can address that. The main difference between speargun and air rifle is weight of projectile; that is nothing but an energy issue that can be addressed by someone with mechanical knowledge, patience, and stuff gathered in a farm or town.

Other thing you could do is use arrows/bolts instead of speargun spears as projectile because of weight and tip options.

Now, the other important question is: can a garden variety speargun you found on an abandoned boat be a postapocalyptic weapon as-is? It depends. Are you trying to reach enemies a mile away? Not a chance on a stock speargun. Throwing a spear or even an arrow at Girandoni's distance will also not be doable with stock speargun. Are you setting said spearguns as traps inside a room like the Rust game? Completely doable.

Using a standard speargun as basis to something more, well, steampunk? Now that is another story; I am picturing now a boiler providing steam for many high pressure reloadable (I think the Chinese did something like that which was crank operated) speargun/ballista-like machines guarding a castle/tower.

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    $\begingroup$ Danke ;) I wanted that weapon for a particularly vile slave trader - if any of the ware escapes, the others would use a whip or bolas to recapture them but this one would simply shoot a spear through the leg of the escapee and pull him back with the cord at the end of the spear. Weapons of the old world are rare and costly but as this man lives for hunting and killing he spends a lot on that equipment. As it's his personal equipment/weapon it should be lightweight and small enough to carry it on his back or belt (not a free-standing ballista) $\endgroup$ – Cee Mon Aug 29 '19 at 12:43
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    $\begingroup$ @cee-mon assuming he wants to to hit within 50m(bola's range about 15m), is able to scavenge some piano wire or strong fishing line, can make/find tips that opens after it goes through flesh (two pieces held by hinge), and is good with slow reload, I think it is doable with a rifle length (1m) weapon with steel tube and reservoir like old paintball at under 10Kg. However, if I was him, I would find a larger reservoir (firefighter) on the back which can go to 3K psi with regulator so he can adjust range/force or do multiple shots. $\endgroup$ – raubvogel Aug 30 '19 at 13:44
  • $\begingroup$ A tip with side hooks that fold in while going through flesh, reopen afterwards and claw into the flesh when pushed back. Would a normal harpoon/spear tip with solid side hooks, that don't fold in, reduce the power or depth of the impact that much? $\endgroup$ – Cee Mon Aug 30 '19 at 15:56
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    $\begingroup$ Probably because the damage to the tissue would be larger if you want it to lock into the target. Think of trying to hang something into a drywall: the proper mounting screws have something that will make the part inside the wall (past the drywall sheet) larger than when it got in so it cannot get out without making a larger hole in the process. Here is a fancier example of the tip I recommend: divingdirect.co.uk/images/products/1329585414-44023600.jpg. You could make it by folding the tabs out of flat steel, drilling a hole through them and spear, and then driving a pin. $\endgroup$ – raubvogel Sep 9 '19 at 2:55

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