A mix of Wild West with sci-fi elements where a character decided that it was a bright idea to have a shaped charge gun to blast people (humans or not) with molten "jets" (the shaped charge doesn't have an actual molten jet, but it is called as such for simplicity reasons).

About the weapon:

This character uses a very smaller version of a shaped charge in a custom gun made from common materials, like an adapted 12 gauge shotgun. The projectile itself is meant to be used against people (or similar), so the range in which its "molten jet"/material being ejected is effective plays a major role on its use.

The Shaped Charge can be made of a small package of gun powder (nitropowder) and the material propelled can be Glass. So, a normal gun with a weird bullet type.

Clarifying: the weapon explodes the shaped charge on its barrel, launching the material, it is not a launcher that delivers a payload containing a shaped charge.

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    $\begingroup$ Are you asking if someone could withstand a carefully focused high explosive used to cut steel, or are you asking the lethal range of such an explosion? We have a strict one question per post policy. Can you edit this post to ask a single question. While you're at it, I'd strongly suggest removing unnecessary images to improves readability $\endgroup$
    – sphennings
    Aug 23, 2022 at 17:27
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    $\begingroup$ You seem to be asking for a range of lethality for a range of weapons. You're obviously aware of the capabilities of the existing weapons, but you provide a range of possibilities for your theoretical weapon. Would a shotgun-delivered explosive penetrator work? Maybe, but it wouldn't be worth it for an unarmored opponent. Way too complex and error prone. Can you launch a linear shape charge any meaningful distance? Again, maybe, but probably not reliably. Too many maybes for a rational answer. $\endgroup$ Aug 23, 2022 at 17:33
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    $\begingroup$ OK, I've retracted my close vote. Note, however, that so long as the range is 6 inches or more it's potentially deadly against humans. Now that we've narrowed the question down to only what you need, it might not need to be asked anymore. This is a completely believable weapon to me. (Note, though, that the way shaped charges in projectile weapons work is that the shaped charge ignites when it hits something, like somebody's chest. So the measurement of "range" is calculated from the point of impact and the average human torso is about one foot thick.) $\endgroup$
    – JBH
    Aug 23, 2022 at 18:27
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    $\begingroup$ You might need to worry about a minimum range, since the similar shotgun shell has one (due to explosion risks). For a sci-fi version of old West, I'd go with the gyrojet en.wikipedia.org/wiki/Gyrojet $\endgroup$
    – DWKraus
    Aug 23, 2022 at 18:36
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    $\begingroup$ Wow, that IS a suicide weapon. Good luck. $\endgroup$
    – DWKraus
    Aug 23, 2022 at 20:57

5 Answers 5


Basically you are asking "What is the effective range of an Explosively Formed Projectile (EFP)?"

Whether or not you hold onto the explosive device is actually not relevant. If you can handwave a handgun that can survive the pressures involved directly, that is an in universe engineering problem.

So, what is the effective range of an EFP? That's a really good question. The physics behind these things is... interesting. Certainly far above my level of understanding, and five minutes of Googling doesn't provide any good answers. Therefore I shall answer based on "what will my suspension of disbelief stand?" (Others will, of course, have different opinions!)

The projectile is effectively a "slug" of molten metal, and I don't think the metal would have time to cool to a solid before reaching the ground or being disrupted by its travel through the air over any reasonable trajectory.

Liquids don't have great cohesion in air, so that is going to be a limiting factor. There are some very expensive water pistols that fire slugs of water. They have an effective range of about 10m/30ft, or perhaps a bit more. Videos I have seen of them look as if the water could go further, but much more than that and its more like a shower than a shot. We can use that as a lower bound. (I'm not saying its right, but for story purposes in a question that doesn't ask for Hard Science, I find it within my suspension of disbelief). Now actually that isn't too bad. Oft quoted statistics suggest that 7m/21ft is actually a typical engagement range for handgun combat.

What about an upper bound? Well, an EFP is obviously much faster that the water pistol above ("sources" suggest 2kps or more), so if the degeneration were purely time based it would go much further. However, that velocity creates more friction with the air that will tend to pull the projectile apart faster. Also I have no idea how well molten metal flying through the air compares to water in terms of its tendency to stick together. Looking at volcanoes, molten rock may be pretty good. Can we extend that to metal? I don't know.

In short I have no idea how to even start modelling this. Given the lower bound and my intuitive experience of the world, I wouldn't say hundreds of meters is believable. Maybe 50 to 100m (150-300ft)? For a cowboy style scientifically plausible blaster pistol (holding onto what is effectively a grenade not withstanding) that may well be good enough.

  • $\begingroup$ Against tank armour, a predetonation 20cm difference is enough to make the shape charge useless. But that's tank armour, not human flesh. $\endgroup$
    – DKNguyen
    Aug 25, 2022 at 0:43
  • $\begingroup$ Yeah but he's talking about an EFP which forms a distinct projectile as compared to the jet formed by a standard shaped charge. So it is effective against even armor at much longer distances. $\endgroup$
    – Niras
    Sep 24, 2022 at 1:51

You shouldn't detonate your shaped charge in the barrel of a gun. If you try that, you'll destroy the gun barrel. You can, in theory, use a shotgun to launch a shaped-charge projectile, but this is quite hard to make effective.

As per this diagram from Wikipedia, your projectile needs a long, but flimsy, pointed nose. This serves two purposes: it makes the projectile aerodynamic, and the trigger on the point is used to fire the shaped charge at the right stand-off distance from the target. You need that stand-off to allow the jet from the shaped charge to form before it starts burning into the target. For extra difficulty, the shaped charge needs to be detonated at its rear, so you need some way to signal along the length of the projectile, very rapidly and very reliably. The diagram suggests a piezoelectric trigger and a wire to the detonator, and that seems as good as anything.

Fitting all of this into something the diameter of a shotgun shell (18.5mm) is quite hard. A design was developed in the early 2000s, but the USMC tested it and did not adopt it. Its usefulness would be confined to getting through body armour: it did less damage than an ordinary shotgun slug. During WWII, the Germans made shaped-charge rounds for the Kampfpistole flare gun, but they were not effective, due to the small calibre (23mm).

If you can use oversize smoothbore guns, like an M79 grenade launcher, shaped charges will be much more effective. Unnecessarily powerful for killing unarmoured humans, but thoroughly effective on armoured humans and combat robots.


What is Old is New Again:

SMALL FRAME CHALLENGE: A weapon that has the explosive explode at the point of firing is pretty much a suicide weapon with insanely short range, OR a mine of some kind. I wrote this answer before the clarification, assuming the shell would explode at the point of impact. I still think it is the only workable solution

A shaped charge creates a high-velocity hypersonic projectile as the explosion crushes a metallic lining into a missile that can penetrate a tiny target. The intense pressure doesn't necessarily liquify the metal, but it can get extremely hot and cause secondary incendiary effects. But a shaped charge begins to come apart after about 2 meters, making it an EXTREMELY short-ranged projectile. the most minute irregularities in the metal or explosive create wild instabilities in the projectile. This is the chief reason a shaped-charge gun doesn't work. Your gun has a range of two meters. Most likely, the shotgun would blow up and the range of such a small shaped charge would likely be shorter than the length of the barrel.

The second reason is that for every action there is an equal and opposite reaction. The explosion goes out the other way. This means the poor person or weapon behind the blast gets horrifically punished.

But there is a tried and true solution - set off the explosion at the destination, not the source. So a shotgun needs to launch a shaped charge to go off at the destination.

Someone has already made something equivalent, the FRAG-12. This very complicated shotgun shell is essentially a tiny version of a rocket-propelled grenade designed to penetrate light armor. Unfortunately, it's very expensive and competes with a lot of dedicated armor-piercing weapons on the military market.

It has a minimum range of three meters, so the explosive doesn't arm and explode too early, killing the shooter. The maximum range of this particular system is 200 meters, but a home-made, improvised device (even with some future tech added) is unlikely to reach these ranges without a rocket-assist.

But with the rocket assist, the sky is the limit - literally. The gyrojet was a rocket-propelled ammunition variant that would lend itself well to sci-fi Western. The guns are smoothbore, there is no significant recoil, the rounds could operate in space (or potentially under water), they look like ray guns, and they could easily leave glowing visible streaks in the air like a 'blaster.' It was available in a flare gun version, which was really a mini rocket launcher, but would support the kind of shells you are looking for. With a range of 460 meters, it was considered for development into a grenade launcher version that would look a lot like the weapon you are thinking of.

Here is a home-made version of a HESH round. The video is a bit underwhelming, but it does have a bigger kick than a regular shotgun shell. A similar round that is spectacular to see is the Dragon's Breath shell, a magnesium incendiary round.

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    $\begingroup$ I honestly thought gyrojets were a fictional technology from the videogame Tiny Tina's Wonderlands! $\endgroup$
    – Tom
    Aug 24, 2022 at 17:27
  • $\begingroup$ @Tom Yeah, they're weird and cool all at once. I've mentioned them in more than one answer. I think they still have a shot (pardon the pun) in a world with drones due to the recoilless nature (to allow small armed flying drones) and ease of use in space combat. $\endgroup$
    – DWKraus
    Aug 25, 2022 at 1:48

I would say "no", unless you have some serious shielding for the hands, arm, chest and face.


The Japanese Lunge mine was mounted on a stick. The soldier held the stick halfway which puts the soldier a bit more than 1m away from the explosion. It was a suicide mine that would kill the user.

The range is probably not very long but I dont know. As a rule of thumb the range through steel armor is 7x the diameter of the charge, but what that means for punching holes in fleshy bits a few meters away I dont know.


Probably pretty short.

Wikipedia mentions that shaped charges "...penetrate armor steel to a depth of seven or more times the diameter of the charge...". I have no idea how to transform that into the range that would still be lethal to a human, so I will assume a factor of 10. To get a rough upper bound I picked the diameter of a hand grenade - of course the real limit is lower since being roughly 1 meter (the length of a shotgun barrel) away from a hand grenade is a rather bad spot. Anyhow, assuming a 8cm diameter, it comes down to a whopping 5.6 meters.

That wouldn't be too bad, but again, this assumes an explosive which would kill the user and probably overstates the lethal range (the factor 10 seems rather generous). Since this answer already contains a lot of speculation on my part (and I don't know the specifics on how-to) I won't try to scale it down, but I'd be surprised if it ends up being more than a meter.


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