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Often in science fiction, we see that there are swords that deflects bullets, almost every single renditions has the sword wielder having hyper reflexes. The undeniably most famous example of this trope is the Star Wars light saber.

Forget about the reflexes a user of this sword would need, assume that I have found Superman or a really cool cyborg. Using modern or near future technology, could I build a sword that stops bullets? What about one that deflects them?

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  • $\begingroup$ I don't know how to believe this guy's skill is real, but he's interesting nonetheless: Isao Machii. $\endgroup$ – Thom Blair III Dec 29 '16 at 8:16
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    $\begingroup$ There were bullets 8n Star Wars? You are comma splicing. $\endgroup$ – JDługosz Dec 29 '16 at 8:28
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    $\begingroup$ depends on the bullet, few mateials will stop 20mm Depleted uranium rounds, certainly none that could be formed into a human-scale sword. $\endgroup$ – Jasen Dec 29 '16 at 9:18
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    $\begingroup$ Actually your StarWars example is somewhat flawed.. Jedi Lightsabers can only really deflect blasterfire. They've a hard time deflecting actual bullets (scifi.stackexchange.com/questions/13695/…) $\endgroup$ – dot_Sp0T Dec 29 '16 at 10:48
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    $\begingroup$ You might want to watch some clips from the show forged in fire, one of their tests for blade makers skill is whether their sword can split a bullet without damage. youtube.com/watch?v=6Hasi-giZck. A well made sword should deflect at least pistol rounds without appreciable damage. $\endgroup$ – John Apr 22 '17 at 15:29
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Wielder's Strength

So your sword wielder has superhuman reflexes, but he'll also need some degree of superhuman strength to hold a bulletproof sword while it deflects a bullet. With that being said, there are a number of materials capable of withstanding bullets:

ALON Transparent Aluminum

Known commercially as ALON, transparent aluminum armor is made of aluminum oxynitride, a combination of aluminum, oxygen and nitrogen. Before it can end up as a hard transparent armor plate, it begins as a powder. This powder is then molded, subjected to high heat and baked, just as any other ceramic is baked. Once baked, the powder liquefies and then quickly cools into a solid, which leaves the molecules loosely arranged, as if still in liquid form. The resulting rigid crystalline structure of the molecules provides a level of strength and scratch resistance that's comparable to rugged sapphire. Additional polishing strengthens the aluminum alloy and also makes it extremely clear.

Now, just as bullet-resistant glass is made of three layers (two panes of glass and a middle pane of polycarbonate), so too is transparent aluminum armor. The three layers, consist of the following:

  • An outer layer that's exposed to gunfire and made of baked aluminum oxynitride

  • A middle layer of glass

  • A rear layer of polymer backing

Not only can the aluminum armor deflect rounds from small-caliber weapons and still be more clearly transparent than bullet-resistant glass that's been shot, it also passes a much more important test -- a 1.6" thick pane resists .50-caliber armor-piercing bullets and anti-aircraft weapons that typically use .30-caliber rounds. This is an impressive feat, especially since it's half the weight and thickness of traditional transparent armor.

So, a 1.6" thick sword is thick, but relatively lightweight, and can stop a direct hit from armor piercing rounds. A thinner version could probably easily stop .22 rounds. So that's one possibility.

Composite Metal Foam

Composite metal foam (CMF) is made by bubbling gas through molten metal to form a frothy mixture which then sets as a lightweight matrix. This leaves a material that offers a lighter alternative to conventional metals, while still maintaining a comparable strength.

CMFs have been used to create high-strength armor comprised of boron carbide ceramics as the strike face, with CMF as the bullet kinetic energy absorber layer and Kevlar panels as backplates. To test its durability, such armor was tested against a 7.62 x 63 mm M2 armor-piercing projectile, which was fired in line with the standard testing procedures established by the National Institute of Justice (NIJ). This armor could stop the bullet at a total thickness of less than an inch, while the indentation on the back was less than 8 mm. In fact, not only did the armor stop the bullet, it turned it into dust. To put that in context, the NIJ standard allows up to 44 mm (1.73 in) indentation in the back of an armor.

So, this type of material could be incorportated into a sword to make sure it was strong enough to deflect or stop bullets. You might need to have a significantly wide sword, depending on how thick the materials are, but a wider sword could still be useable.

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    $\begingroup$ Is steel not an option? Also, how strong does the wielder need to be? Assuming typical length sword with a bullet hitting mid-length. $\endgroup$ – Samuel Dec 29 '16 at 8:39
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    $\begingroup$ to get the sword infront of the bullet requires superhuman stregth, holding the sword not so much, - Mythbusters did an investigation into "shoot gun out of hand" that may be useful. $\endgroup$ – Jasen Dec 29 '16 at 9:14
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    $\begingroup$ you can't just "Plate" ALON onto your sword. And no, a .22 could not be "easily stopped" by a "thinner plate" because that's not how ALON (or any bullet proof glass) works. Have a look at this link, and you'll quickly realize that plating ALON would not only make your sword really heavy and thick in addition to the original materials required, but your sword will also quickly become unbalanced as it stops more bullets. $\endgroup$ – Aify Dec 29 '16 at 18:08
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    $\begingroup$ This isn't quite what the OP is asking. The sword doesn't need to withstand the full force of a bullet, because it's not stopping it, it's deflecting it. Ideally, the bullet would strike the sword at a grazing angle (maybe 20 degrees?) sufficient to cause the bullet to pass to one side. Not much different in principle from parrying a sword stroke: it takes much less force to parry than to block. Indeed, you can parry a steel katana with a wooden bokken - at least if you're Miyamoto Musashi :-) $\endgroup$ – jamesqf Dec 30 '16 at 4:54
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    $\begingroup$ You dont need superhuman strength to stop a bullet. The amount of recoil the shooter experiences is the amount of "recoil" the swordwielder will experience upon blocking the bullet. So unless it's a mounted weapon or similar you only need superhuman strength to move the weapon in position, assuming the sword is heavy. As a future material a Graphene alloy, both light and many times stronger than steel, and can have a far better edge. Assuming Graphene can ever be produced in bulk in specific shapes $\endgroup$ – Demigan Sep 4 '18 at 17:41
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The Jedi may have fast reflexes, but their ability to block lasers is because they have an intuitive feeling of what will happen in the future a few seconds, so they actually predict where the laser will be. It would be totally impossible to 'react' to a laser shot. The laser travels at the speed of light, therefore by the time you have seen the laser it has already reached you. If you could see the person firing, you could see them point the weapon and start tightening their finger on the trigger, but once the laser has fired it's too late. For anything slower than a laser, you would still basically need to be a robot (electrical signals to control) to react in time. It takes time for signals to travel from a human brain to their muscles. Or from eyes to brain. I guess if you were hitting bullets to the side that should work fine- striking them directly and bouncing them back would, as mentioned, transfer force to the defender, but just pushing them off-course wouldn't transfer much of their energy.

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    $\begingroup$ It's kind of why star wars "lasers" are closer to plasma bolts. They even made a nod to this in The Force Awakens in the bolt that Kylo Ren stops in the first scenes. The shape it takes mimics a research to similar events that was conducted. Cant find it right now I'll look for it. $\endgroup$ – Demigan Sep 4 '18 at 17:50
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Yes with today's technology and even tech from the early 1900s if not later, you could build a sword able to withstand bullets, depending on the bullet and construction of the sword. Your main issues are going to be what caliber the bullet is, and how much the sword is going to be damaged.

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Jedis (and Sith) don't really have superhuman reflexes, at least in a regards to intercepting blaster fire.

"The average for these things is just 34.9 m/s (78 mph). This is in the ballpark of a baseball pitch."

https://www.wired.com/2012/05/star-wars-blaster-speed/

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If we were to create a sword for the sole purpose of deflecting bullets, I would argue for a differently designed sword rather than a special material. A sword with wider blade Machete-style, would give an increased surface area for better being able to hit your bullets. Bullets already easily ricochet off surfaces that are angled. All you need to do is get this wider weapon to angle correctly and Bingo!

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A giant manga sword is as thick as battleship plating and easily big enough to hide behind in a gun fight.

enter image description here

Carrying it could be a problem let alone using it in a fight......

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Probably not

There are definitely materials which can withstand bullets. There are several answers which go over this aspect of the question, and there are definitely materials which can withstand impact from a bullet. There is still a problem, though:

Bullet strength

Assuming these are normal bullets, if the material is rigid, the bullet will either deform or shatter. Deflecting a bullet would involve slowing it down to speeds such that the bullet is not destroyed, and then re-accelerating it in the other direction, something simple rigid materials cannot accomplish.

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Sword can be easily made to be resistant enough, at least for small calibre rounds. The problem is, when it's hit, your arm will have hit force applied to it too, and at best! you will lose your grip on the sword. At worst, your fingers might end up broken. Modern bullets carry really high forces that translate to the target.

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    $\begingroup$ Can explain how people firing handguns don't break their hands then? $\endgroup$ – sphennings Apr 22 '17 at 14:05
  • $\begingroup$ Remember that mostly any weapon has its recoil compensated by the weapon mechanism itself (and any built-in compensation mechanisms, either passive, or active ones). True, the 9mm para round hitting your blade will not harm you MUCH (but you will still feel it in your hand), but a .50 AC round could well do damage - remember that some heavy rewolvers are able to damage your wrists if you try to shoot them one handed, or handle the shoot improperly, and thats while having a barrel-mounted recoil compensator! $\endgroup$ – Michał Jastrzębski Apr 22 '17 at 16:06
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In short, yes - why not?

Swords are very hard and very strong - and if you're trying to deflect a bullet rather than stopping it, a strong piece of metal held at an angle should do the trick quite nicely! If the sword is likely to be used for deflecting many bullets then you might want to look into specialised materials and clever metallurgy.

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