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I used to think that the most dangerous thing about the AR-15 was that it had the capacity to hold 30 round magazines. I don't have a good opinion of 100 round

by a_p 14y ago

I used to think that the most dangerous thing about the AR-15 was that it had the capacity to hold 30 round magazines. I don't have a good opinion of 100 round drums, because they jam too easily. Then I learned about the Slide Fire [1], a stock that legally gives the AR-15 full auto capability. The loophole is that the stock uses the gun's recoil to pull the trigger again, instead of the gun's internal mechanism doing it. A good analogy to computers would be an interface that does not allow clicking a button to send multiple requests, but allows a script to click the button much faster than a human would. [1] http://www.slidefire.com/ http://www.slidefire.com/

nthj 14y ago
> I used to think that the most dangerous thing about the AR-15 was that it had the capacity to hold 30 round magazines Yep. I'm gonna feel so much safer when I'm murdered with ten 9mm bullets instead of seventeen. Oh wait, not so much.
- a_p 14y ago
  An automatic rifle is much more dangerous than an automatic handgun, because of the physics involved. When a bullet enters yours body, the rapid deceleration of the bullet creates a shock wave that creates a micro-cavity in your body that lasts for milliseconds. This micro-cavity does enormous damage to your internal organs. That is why rifles (which fire bullets with much more kinetic energy) are so much more dangerous than pistols. In general, you are much more likely to survive multiple pistol wounds than you are multiple rifle wounds. Sidenote: Rifles used in the Civil War and modern rifles fire bullets with roughly the same kinetic energy. Improvements to gunpowder have allowed smaller bullets to be fired with larger velocity.
  - hga 14y ago
    There is a great deal of argument over that theory of terminal ballistics vs. the "permanent crush cavity" favored by Dr. Martin Fackler, who I follow. I'm sure some organs are subject to serious damage that way, but he believes that in general tissue is fairly willing to be pushed and squeezed and snap back, without significant damage compared to what is crushed. He's also the guy who figured out the significant wounding mechanism of the original AR-14/M16 FMJ bullet: if it hits at enough velocity, as it tumbles the bullet breaks at the cannelure. The higher the velocity, the more the back half disintegrates. Now, he was doing this in calibrated ballistic gelatin, but it seems to match the observed in the field results, which is how he got started in all this as a battlefield surgeon.
    - a_p 14y ago
      Thank you for this information. One of the difficulties of research in this field is that acceptable tests materials (gelatin blocks) have different densities and structures then battlefield targets. Out of curiosity, what would be the characteristics would be for ammunition that is designed to inflict damage on non-organic targets of almost uniform density? In other words, ammunition that is designed to destroy the steel or aluminum of airplanes or buildings.
      - hga 14y ago
        Aluminum strikes me as a very poor choice, one reason it's so popular is it's strength to density ratio, i.e. it's a lightweight metal. It's also catches on fire very easily, is the fuel in typical thermite and and various rocket motors including the Space Shuttle Solid Rocket Booster, and pretty clearly played a role in the Hindenburg disaster (hydrogen doesn't burn like that). It has a role in e.g. GAU-8 (A-10's) PGU-14/B ammo, cast around a depleted uranium perpetrator, acting somewhat like a sabot in allowing the bullet to be lighter in weight and therefore faster, but outside of that sort of thing I don't see it having a role in ammunition.
        a_p 14y ago
        What I meant to ask is whether there is a type of ammunition that is specifically designed to damage a structure (the structure is what might be made out of a metal or metal alloy, or something else such as kevlar) rather than cause physiological damage. I wasn't suggesting that aluminum is a good material for a bullet. Bullets that are designed to fragment upon impact because this causes damage to living things. My question is whether frangibility is desired when the purpose is to cause the most structural damage, e.g when the target is an airplane or tank. I suppose depleted uranium or tungsten carbide bullets match this description, because they are designed to go through armor before they start to disintegrate. But these types of bullets are still meant to eventually hit humans.
        hga 14y ago
        Actually, most non-FMJ bullets who's targets include animals including humans aren't designed to fragment on impact, but to expand, and therefore transfer more of their energy to the target once they get inside. The useful fragmenting of the latter half of M16 FMJ ammo was unknown until Martin Fackler conclusively demonstrated it in the '80s, a couple of decades after its design. And we've switched bullets since then (see below), although the new one is thought to have the same wounding mechanism. It's "useful" because all that, the breaking in half and possibly fragmenting, provides much more stopping power to an otherwise not very effective round. If that doesn't happen, the effect is more like getting stuck with a pencil, except that the bullet will turn 180 degrees and likely exit back first; the M16 is infamous for inconsistent stopping power. Note that according to the Hague Convention, our military isn't allowed to design bullets to do this.... Fragmentation is very much not a desired feature for creating any type of structural damage; there you want all energy possible to be transmitted to the target. Even expansion is undesired, because the physical work done to deform the bullet is not available to penetrate the structure and then do further damage once past it. This often gets into the realm of armor piercing (AP) ammo, which has steel or harder metals inside the bullet, sometimes comprising almost all of it, sometimes as a smaller penetrator, like the steel rod inside the .30-06 ammo that I've read became the standard for the US towards the end of WWII (although that was in part because steel was cheaper than lead), or the steel pellet that's in the 5.56 NATO SS109, M855 green tip for the US, design bullet (which is really machine gun ammo/designed to satisfy a silly requirement of piercing a metal helmet at a very long distance, it's not really good ammo for rifles for a whole bunch of reasons). With the exception of 5.56 NATO AP, there should be no differences in wounding capability, larger caliber bullets don't depend on deformation for wounding. Our M995 black tip ammo ... well, look at this picture: http://www.ar15.com/archive/topic.html?b=3&f=16&t=562820 http://www.ar15.com/archive/topic.html?b=3&f=16&t=56... I assume the bullet is not as likely to break at the cannelure, that the aluminum boot in which it sits is no more likely to cause damage ... but that would have to be tested. Certainly gunners would try to avoid wasting ammo by using AP on humans.... Then we get to exotic stuff that includes an explosive payload, normally 20 mm ammo and above, generally intended for aircraft until we get into serious anti-armored vehicle ammo. You're really not supposed to use that on humans, but of course that's not so well observed in wars. And there's this exotic and inherently expensive .50 BMG round that's intended to provide the destructive power of a 20 mm shell: http://en.wikipedia.org/wiki/Raufoss_Mk_211 http://en.wikipedia.org/wiki/Raufoss_Mk_211 ; see the Legality section on expected effects on humans.
jbooth 14y ago
So, the military teaches troops to almost never use full-auto on their rifles. Why is having full-auto mode so much more dangerous? Seems that in a mass-shooting situation, the person's more likely to blow the whole clip and be out of ammo.
- a_p 14y ago
  In a firefight between two militaries, it is not more dangerous. The danger is that the regular police that only carry sidearms would be seriously outgunned.
  - jff 14y ago
    Not really. The point is that in fully automatic mode, you can blow through a backpack full of ammunition in about a minute, probably not hitting anything because the continual fire and your efforts to control the gun are throwing the barrel all over the place. Now the cops are standing there, they're pissed, and you're out of ammunition. If you were a typical "crazed killer", this is the point where you'd shoot yourself, but you just sprayed all your bullets down the street.
    - a_p 14y ago
      Bump firing the rifle would be inaccurate if the shooter went through the whole clip with one or two pulls. This stock attachment allows for reasonably accurate burst firing. A gunman with an automatic weapon will not necessarily waste all of his ammunition with continuous, inaccurate fire. With very little training, he can learn to burst fire. This capability blurs the line between a military and civilian rifle. There is a video of the stock in action here [1]. It seems to me that someone with limited training would still completely outgun a regular police officer armed only with a pistol. [1] http://www.youtube.com/watch?v=dvLt8-Wf7r0 http://www.youtube.com/watch?v=dvLt8-Wf7r0
      - jbooth 14y ago
        ... so? If someone is well enough trained to fire controlled bursts, they're probably well enough trained to be just as effective double tapping in semi-auto.
jff 14y ago
Full auto is frankly a stupid feature. It wastes ammunition, it's inaccurate. There is a reason soldiers rarely use fully-auto except in specific circumstances. Bump firing, which is what the Slide Fire does, is even worse because it throws your accuracy to utter hell--look up the Wikipedia article (http://en.wikipedia.org/wiki/Bump_fire http://en.wikipedia.org/wiki/Bump_fire) Oh, and most rifles with removable magazines can accept 30 round magazines, it's not a magical AR-15 capability.
jonnycoder 14y ago
Here is some more perspective on high capacity magazines. Regular 9mm Glocks and Berettas such as Glock 17 and Beretta 92fs are designed to hold 17 or 15 round magazines, stock. The FN 5.7, the same gun used in the Fort Hood shooting and also reported to be in use by Secret Service, and legal for citizen ownership, has a 20 round stock magazine. The California legal version requires a 10 round magazine.

by a_p 14y ago

nthj 14y ago

> I used to think that the most dangerous thing about the AR-15 was that it had the capacity to hold 30 round magazines Yep. I'm gonna feel so much safer when I'm murdered with ten 9mm bullets instead of seventeen. Oh wait, not so much.

a_p 14y ago
An automatic rifle is much more dangerous than an automatic handgun, because of the physics involved. When a bullet enters yours body, the rapid deceleration of the bullet creates a shock wave that creates a micro-cavity in your body that lasts for milliseconds. This micro-cavity does enormous damage to your internal organs. That is why rifles (which fire bullets with much more kinetic energy) are so much more dangerous than pistols. In general, you are much more likely to survive multiple pistol wounds than you are multiple rifle wounds. Sidenote: Rifles used in the Civil War and modern rifles fire bullets with roughly the same kinetic energy. Improvements to gunpowder have allowed smaller bullets to be fired with larger velocity.
- hga 14y ago
  There is a great deal of argument over that theory of terminal ballistics vs. the "permanent crush cavity" favored by Dr. Martin Fackler, who I follow. I'm sure some organs are subject to serious damage that way, but he believes that in general tissue is fairly willing to be pushed and squeezed and snap back, without significant damage compared to what is crushed. He's also the guy who figured out the significant wounding mechanism of the original AR-14/M16 FMJ bullet: if it hits at enough velocity, as it tumbles the bullet breaks at the cannelure. The higher the velocity, the more the back half disintegrates. Now, he was doing this in calibrated ballistic gelatin, but it seems to match the observed in the field results, which is how he got started in all this as a battlefield surgeon.
  - a_p 14y ago
    Thank you for this information. One of the difficulties of research in this field is that acceptable tests materials (gelatin blocks) have different densities and structures then battlefield targets. Out of curiosity, what would be the characteristics would be for ammunition that is designed to inflict damage on non-organic targets of almost uniform density? In other words, ammunition that is designed to destroy the steel or aluminum of airplanes or buildings.
    - hga 14y ago
      Aluminum strikes me as a very poor choice, one reason it's so popular is it's strength to density ratio, i.e. it's a lightweight metal. It's also catches on fire very easily, is the fuel in typical thermite and and various rocket motors including the Space Shuttle Solid Rocket Booster, and pretty clearly played a role in the Hindenburg disaster (hydrogen doesn't burn like that). It has a role in e.g. GAU-8 (A-10's) PGU-14/B ammo, cast around a depleted uranium perpetrator, acting somewhat like a sabot in allowing the bullet to be lighter in weight and therefore faster, but outside of that sort of thing I don't see it having a role in ammunition.
      - a_p 14y ago
        What I meant to ask is whether there is a type of ammunition that is specifically designed to damage a structure (the structure is what might be made out of a metal or metal alloy, or something else such as kevlar) rather than cause physiological damage. I wasn't suggesting that aluminum is a good material for a bullet. Bullets that are designed to fragment upon impact because this causes damage to living things. My question is whether frangibility is desired when the purpose is to cause the most structural damage, e.g when the target is an airplane or tank. I suppose depleted uranium or tungsten carbide bullets match this description, because they are designed to go through armor before they start to disintegrate. But these types of bullets are still meant to eventually hit humans.
        hga 14y ago
        Actually, most non-FMJ bullets who's targets include animals including humans aren't designed to fragment on impact, but to expand, and therefore transfer more of their energy to the target once they get inside. The useful fragmenting of the latter half of M16 FMJ ammo was unknown until Martin Fackler conclusively demonstrated it in the '80s, a couple of decades after its design. And we've switched bullets since then (see below), although the new one is thought to have the same wounding mechanism. It's "useful" because all that, the breaking in half and possibly fragmenting, provides much more stopping power to an otherwise not very effective round. If that doesn't happen, the effect is more like getting stuck with a pencil, except that the bullet will turn 180 degrees and likely exit back first; the M16 is infamous for inconsistent stopping power. Note that according to the Hague Convention, our military isn't allowed to design bullets to do this.... Fragmentation is very much not a desired feature for creating any type of structural damage; there you want all energy possible to be transmitted to the target. Even expansion is undesired, because the physical work done to deform the bullet is not available to penetrate the structure and then do further damage once past it. This often gets into the realm of armor piercing (AP) ammo, which has steel or harder metals inside the bullet, sometimes comprising almost all of it, sometimes as a smaller penetrator, like the steel rod inside the .30-06 ammo that I've read became the standard for the US towards the end of WWII (although that was in part because steel was cheaper than lead), or the steel pellet that's in the 5.56 NATO SS109, M855 green tip for the US, design bullet (which is really machine gun ammo/designed to satisfy a silly requirement of piercing a metal helmet at a very long distance, it's not really good ammo for rifles for a whole bunch of reasons). With the exception of 5.56 NATO AP, there should be no differences in wounding capability, larger caliber bullets don't depend on deformation for wounding. Our M995 black tip ammo ... well, look at this picture: http://www.ar15.com/archive/topic.html?b=3&f=16&t=562820 http://www.ar15.com/archive/topic.html?b=3&f=16&t=56... I assume the bullet is not as likely to break at the cannelure, that the aluminum boot in which it sits is no more likely to cause damage ... but that would have to be tested. Certainly gunners would try to avoid wasting ammo by using AP on humans.... Then we get to exotic stuff that includes an explosive payload, normally 20 mm ammo and above, generally intended for aircraft until we get into serious anti-armored vehicle ammo. You're really not supposed to use that on humans, but of course that's not so well observed in wars. And there's this exotic and inherently expensive .50 BMG round that's intended to provide the destructive power of a 20 mm shell: http://en.wikipedia.org/wiki/Raufoss_Mk_211 http://en.wikipedia.org/wiki/Raufoss_Mk_211 ; see the Legality section on expected effects on humans.

jbooth 14y ago

So, the military teaches troops to almost never use full-auto on their rifles. Why is having full-auto mode so much more dangerous? Seems that in a mass-shooting situation, the person's more likely to blow the whole clip and be out of ammo.

a_p 14y ago
In a firefight between two militaries, it is not more dangerous. The danger is that the regular police that only carry sidearms would be seriously outgunned.
- jff 14y ago
  Not really. The point is that in fully automatic mode, you can blow through a backpack full of ammunition in about a minute, probably not hitting anything because the continual fire and your efforts to control the gun are throwing the barrel all over the place. Now the cops are standing there, they're pissed, and you're out of ammunition. If you were a typical "crazed killer", this is the point where you'd shoot yourself, but you just sprayed all your bullets down the street.
  - a_p 14y ago
    Bump firing the rifle would be inaccurate if the shooter went through the whole clip with one or two pulls. This stock attachment allows for reasonably accurate burst firing. A gunman with an automatic weapon will not necessarily waste all of his ammunition with continuous, inaccurate fire. With very little training, he can learn to burst fire. This capability blurs the line between a military and civilian rifle. There is a video of the stock in action here [1]. It seems to me that someone with limited training would still completely outgun a regular police officer armed only with a pistol. [1] http://www.youtube.com/watch?v=dvLt8-Wf7r0 http://www.youtube.com/watch?v=dvLt8-Wf7r0
    - jbooth 14y ago
      ... so? If someone is well enough trained to fire controlled bursts, they're probably well enough trained to be just as effective double tapping in semi-auto.

jff 14y ago

Full auto is frankly a stupid feature. It wastes ammunition, it's inaccurate. There is a reason soldiers rarely use fully-auto except in specific circumstances. Bump firing, which is what the Slide Fire does, is even worse because it throws your accuracy to utter hell--look up the Wikipedia article (http://en.wikipedia.org/wiki/Bump_fire http://en.wikipedia.org/wiki/Bump_fire) Oh, and most rifles with removable magazines can accept 30 round magazines, it's not a magical AR-15 capability.

jonnycoder 14y ago

Here is some more perspective on high capacity magazines. Regular 9mm Glocks and Berettas such as Glock 17 and Beretta 92fs are designed to hold 17 or 15 round magazines, stock. The FN 5.7, the same gun used in the Fort Hood shooting and also reported to be in use by Secret Service, and legal for citizen ownership, has a 20 round stock magazine. The California legal version requires a 10 round magazine.