'Shotguns have dkb/dbt' - where did that myth (?) come from?
 

Greetings, all!

Several times in my life I've encountered the opinion that shotgun attacks have so much 'push' that despite not penetrating the armour (vest or whatever), the blast is enough to break ribs, cause internal bleeding etc. I've even heard of an 'advanced' bulletproof vest which was made not only hard but heavy specifically to resist this 'shock'. I think this is wrong, judging by many posts of the local guns experts, but of course I could've misinterpreted them.

So it's a myth, right? Where did it come from, especially the 'shot-proof vest'?

Thanks in advance!

Re: 'Shotguns have dkb/dbt' - where did that myth (?) come from?
 

Movies.

You can really see this, for example, in Hard Boiled.

Re: 'Shotguns have dkb/dbt' - where did that myth (?) come from?
 

Any firearm has the potential for that sort of thing. Shotguns just tend to pack more energy into the whole, personally I think a lot of it is wasted with pellet dispersal, or something.

Anything that completely stops the projectile(s) will absorb that energy. Pistol rounds into a bullet proof vest will do it as well, there's just a lot less energy to start with. (All you guys with the slide rules, calm down. All I'm saying is there's a lot more propellant in a 12g shell than a 9mm cartridge.)

I guess there are two factors:
1) How flexible the armor is. I've worn Vietnam-era flak jackets, and trust me, nothing that you will survive is likely to do blunt trauma through it.
2) How powerful the round is. A .50 Browning round is gonna hurt through even semi-flexible armor. In fact, that one might actually hurt through a half inch of solid steel, because if you aren't using the armor piercing (which will go through that like a hot knife through butter) it *will* bend the steel, making it semi-flexible, at least for that round. A 9mm barely hurts through clothes (my opinion- it definitely makes a hole, I'm just saying the contusions from non-penetrating wounds is way low compared to the bloody part).

I've had .38's, almost the same as 9mm but a bit more powerful, actually bounce off of plywood. From the same range, a shotgun will rip a hole the size of a baseball or softball (depending on other factors). Bottom line is, with enough energy, any round will do what you're saying. Shotguns are just the most likely culprit, because handguns are wimpy compared to long guns, and people tend to use shotguns much more than high (super?) powered rifles. (Note I'm talking something above normal military calibers, perhaps sniper size for long ranges. Normal hunting rounds would likely be a little less energy than shotguns, but that energy would be delivered at about the same amount at a much greater range.) Range is also a factor, if you've ever looked at the way bullet resistant vests are rated, they mention it was tested and able to stop X caliber at Y distance. So while they say 'able to stop a shotgun', it's more a measure of overall performance, with shotgun being at the top of the list of likely threats. I have never seen one say 'able to stop high-powered rifles', because when you start getting into the high end of the performance there, you can get into some hugely powerful stuff that you can't stop without boiler plate. (Like the .50 armor piercing where even 1" of solid steel just won't work.)

Re: 'Shotguns have dkb/dbt' - where did that myth (?) come from?
 

A 28 gram shotgun slug striking at 500 m/s will have 3,500 J of kinetic energy and 14 N-s of momentum.

The 7 kg arm of a karate master punching at 7 m/s will have 170 J of kinetic energy and 49 N-s of momentum. Top karate experts can go a bit faster, up to 10 to 15 m/s, for a maximum of perhaps 100 N-s and 700 J of kinetic energy. A boxing champion (Rocky Marciano) once has the energy of his punch measured at 1250 J using a ballistic pendulum.

Very roughly, momentum is what pushes things around, and energy is what stretches, tears, and breaks things. A punch will push someone around more than a shotgun slug, but even if stopped by a ballistic vest, the energy of the impact will still be able to break things much better than a punch - by about an order of magnitude. It is estimated that a leg bone takes about 350 J to break, an arm bone about 90 J, and a rib bone perhaps 30 J. So a strike by a shotgun slug stopped by a ballistic vest can still smash plenty of ribs.

That is assuming that the energy is efficiently transferred from the slug to the ribs. Trauma plates can distribute the energy over a wider area, and padding and stretchy Kevlar fibers can use up some of that energy before it gets to the torso. I suspect you are still looking at bruising and cracked ribs, though, even if your chest isn't caved in.

However, the paucity of momentum compared to a punch means that a shotgun slug will not be particularly good at knocking people over. They might, however, drop to the ground from pain after getting their ribs smashed up.

Luke

Re: 'Shotguns have dkb/dbt' - where did that myth (?) come from?
 

Um...wow. 7 kilogram arms? I think you're vastly overestimating the weight of the arm, particularly the amount of the arm which is actually moving at peak speed; based on how much water I displace when I put my arm in a container of water, the forearm is maybe 1 kilogram. For reference, knife-proof vests are generally normalized for a 40J impact, which is more than most people can actually deliver.

Of course, knocking someone back with a punch also pretty much doesn't happen, unless they fall over from the shock. About the only impacts which realistically cause any level of knockback are collisions or other similar attacks which involve the full body weight behind the blow.

Re: 'Shotguns have dkb/dbt' - where did that myth (?) come from?
 

My biomech is pretty rusty, but IIRC the torso is 40% and arms are 9% the weight of the human normally.

I'm also surprised that a punch of a respectable combatant is less than 10m×s^-1.

Re: 'Shotguns have dkb/dbt' - where did that myth (?) come from?
 

Depends on what you count as being the arms, but in any case, that would give 7 kilograms for both arms put together, and at that weight probably includes upper arms and shoulder, which aren't really part of the impact mass of a punch.

Re: 'Shotguns have dkb/dbt' - where did that myth (?) come from?
 

A well-delivered punch shouldn't just use the mass of the arm, should it? I'd think a power punch would involve putting the torso behind the blow rather than just the arm - or at the very least, the shoulder.

Then again, I haven't practiced any martial arts in over thirteen years and the only time I punched anything since then I broke one of my fingers, so I'm not exactly an expert.

Re: 'Shotguns have dkb/dbt' - where did that myth (?) come from?
 

Yes and no. An arm by itself is (for simplicity, if not anything else) considered as the part which moves when the torso is fixed, i.e. everything from the shoulderjoint. But the thing is, a punch doesn't involve just the arm moving. It involves the torso turning, a large aid from the hips, and (assuming something like [url=http://www.youtube.com/watch?v=WcsqA4ncnzYoi-zuki[/url] [watch near the very end]) a long step forward.

Re: 'Shotguns have dkb/dbt' - where did that myth (?) come from?
 

A well-delivered punch involves torso muscles, but the actual impact mass is much smaller. Essentially, a punch uses a mechanism very similar to a whip crack to transfer rotational energy generated in the hips and torso into hand velocity, but the mass which is actually relevant for knockback purposes is only the hand and for some types of strike the forearm.

Re: 'Shotguns have dkb/dbt' - where did that myth (?) come from?
 

Usual estimates for punches assume about 1/6 the striker's mass, if the striker is leaning into the blow. Good punches aren't "whip cracks" that channel tons of energy into a hand. Good punches are closer to battering rams that have the entire arm, shoulder, and upper quarter of the torso behind them. An uppercut can do significantly better.

Re: 'Shotguns have dkb/dbt' - where did that myth (?) come from?
 

What would be the in-game difference between the two? One as a Defensive Attack or what?

Re: 'Shotguns have dkb/dbt' - where did that myth (?) come from?
 

There have been many cases of police or other law enforcement getting hit multiple times in a vest and having to be treated for internal bleeding from the impact of a hand gun at close range. as well as cracked ribs and a lot of bruising.

I think the myth is that wearing a vest allows the wearer to just keep taking hits like he is superman.

But then again look at the bank robbery in Hollywood a few years back. guys with layered heavy armor. Video

Then again this was what allowed the police there to start carrying AR-15s.

Re: 'Shotguns have dkb/dbt' - where did that myth (?) come from?
 

In that case, reduce the '7 m/s' figure to 2-3 m/s, since your torso velocity is going to be around your step velocity and your shoulder velocity isn't going to be dramatically higher. There's a lot of options for how the energy is delivered, but the total impact energy is going to be in the 25-50J range for an average person.

Re: 'Shotguns have dkb/dbt' - where did that myth (?) come from?
 

Um, I'm not expecting the bulletproof vest to be bulletproof. But there seems to be an opinion that shotguns do 90% of their damage without penetrating the vest at all through the sheer 'crush' (against which vests supposedly offer no meaningful protection), unlike single-ball weapons which do most of their damage through penetration or 'pierce' (to use GURPS terminology).

Re: 'Shotguns have dkb/dbt' - where did that myth (?) come from?
 

Wrong again, I think. There's step velocity, relative to which there is the relative torso velocity, relative to which is the relative arm velocity. It all adds up.

Re: 'Shotguns have dkb/dbt' - where did that myth (?) come from?
 

I don't disagree. What's important is really more the momentum difference . . . 1 kg at 7 m/s is 7 kg-m/s, while closer to 12 kg at 2 to 3 m/s is 24 to 36 kg-m/s, which is enough to make a 72-kg man stumble. A significant part of the self-defense value of a well-thrown punch is that it pushes the assailant away, regardless of whether it hurts him.

Re: 'Shotguns have dkb/dbt' - where did that myth (?) come from?
 

Also to be remembered is that knock back is a phenomenon that emerges out of the attacker being well anchored vs. a target who is not. Although conservation of momentum and Newton's laws apply, a good punch, kick, or shotgun blast will typically come from someone who is expecting the momentum and whose center of gravity is placed over their foot (feet) and whose body is braced to absorb the momentum of the attack. Meanwhile, the target is not necessarily prepped to receive the jolt of momentum, and so can be knocked down or back because of it.

I've seen Muay Thai and Savate kicks that can accomplish quite a bit of knockback. I can only assume that a shotgun might be able to accomplish similar momentum.

Re: 'Shotguns have dkb/dbt' - where did that myth (?) come from?
 

Opinions are like fundamental orifices. Everyone's got one.

That doesn't change the fact that a ball of roughly .33 caliber travelling at low pistol speeds will perform poorly against body armour. And adding eight more similar balls won't magically make any of them perform better (and the odds of them impacting at precisely the same spot are minimal).

A tactical vest that's proofed against 9mm will also protect against anything up to triple-ought buckshot. Depending on design, it may leave broken ribs or it may be difficult to even notice during an adrenaline-charged encounter. Needless to say, vests of the former design will have a poor reputation with actual operators and will usually not be issued to police or military.

Re: 'Shotguns have dkb/dbt' - where did that myth (?) come from?
 

A shotgun slug is nearly an ounce of metal traveling at the speed of sound or faster. That might break ribs, might.

try this link, box of truth to see what 12g vs 3a vest is like


That doesn't mean the guy on the receiving end of things will even feel it to till the fights over though. buckshot won't go through soft armor or do the job well.

Re: 'Shotguns have dkb/dbt' - where did that myth (?) come from?
 

Incidentally, it's not unreasonable to say that a shotgun slug has twice the knockback of a rifle bullet with comparable damage; it's very likely true. It's just that neither weapon has meaningful levels of knockback.

Re: 'Shotguns have dkb/dbt' - where did that myth (?) come from?
 

Here is a police training video that covers everything you might want to know about shotgun ammuntion including the oddballs.

The only thing not covered was AP slugs vs body armor as I suspect that made the cops queasy

Re: 'Shotguns have dkb/dbt' - where did that myth (?) come from?
 

Fundamentally no gun causes significant levels of knock back.

Simple rule of conservation of momentum and energy.

Every force that a bullet has is given to it in the moment of firing. As momentum at that point must be conserved the amount of knock back a round has is equal to its recoil.

So unless you can see the firer flying backwards will smith style (from Men in Black) the gun is not going to have significant knock back. Of course this is still able to trip people if they do not have good footing same as if you try and fire a shot gun without properly bracing.

As for broken ribs etc. Concealable vest - good approximate for a modern bulletproof without plates etc. Is DR 12 against the average damage of a rifled slug for a shoty (either because they were firing them or as gurps models a close quarters blast from a buckshot) is 18. Thus 6 (12 considering the pi++ bit) points would go through a major wound at minimum and more than enough to cause a few broken ribs.

Else the 2 points of bruising it causes could also cause broken rib or two. Most hospitals would consider someone with a broken rib or two to be in the Good category of injury in the GURPS campaigns (page 421) which is someone with HP over 50% but less than 100%.

End of the day what the injury is specifically is flavor added by the GM. So id sat GURPS already supports what you have said.

Re: 'Shotguns have dkb/dbt' - where did that myth (?) come from?
 

SimonAce, that website has another test (test #3, the wall penetration test for shotgun ammunition loads) which includes this "unofficial" finding:

:D

Re: 'Shotguns have dkb/dbt' - where did that myth (?) come from?
 

Glitterboy, anyone?

Re: 'Shotguns have dkb/dbt' - where did that myth (?) come from?
 

According to that fascinating site, BoxOfTruth, shotguns can be superior to both pistols and rifles (both assault and full calibers)... but only in very specific circumstances.

Penetrating body armor and penetrating walls (this thread topic) - about the same as pistols:
Poorest: buckshot pellets. Minor: pistol rounds, shotgun slug. Major: assault rifles. (Bricks stopped all rounds after a few walls.) The AK-47's 7.62mm round caused the nastiest looking hole in the clay behind the body armor.

Good for: shooting straight into a padlock:
Poorest: Pistol, buckshot. Minor: rifle rounds (drilled straight through cleanly, locks generally still in working order). Major: shotgun slugs (broke the padlock in two).

Good for: shooting against "bulletproof glass" (actually 1.25 inch thick Polycast acrylic, a type of plastic, not glass):
Poor: Pistol, buckshot, assault rifle, and rifle rounds all failed to penetrate. Major: shotgun slugs (penetrated the glass easily).

So it seems shotgun slugs do have a limited range of specialized roles. But usefulness against body armor is not one of them.

Re: 'Shotguns have dkb/dbt' - where did that myth (?) come from?
 

A quick check of my bookmarks shows this:
"Stabbing:
Underarm: up to 63 J
Overarm: up to 115 J
(These are maximum values. PSDP testing suggests that a stab resistant vest rated at 43 joules should be able to stop stabs from 96% of the male population. These standards assume typical commercial knife handles. A fighting handle with a well designed guard to prevent slipping might add another 5 J to the effective attack."
from http://willscommonplacebook.blogspot...vs-muscle.html
I haven't checked the references, use at your own risk.

Luke

Re: 'Shotguns have dkb/dbt' - where did that myth (?) come from?
 

I make use of two techniques, and call them Forearm Strike and Shoulder Bash (Incidentally, This is Mechanic-from-Reality here!). As near as I can determine, FS deals double Thrust damage for purposes of knockback, but half damage for purposes of HP loss (the attack deals 2d, with a 1/4 multiplier after determining knockback, averaging a bit under 2 listed damage, but 7 average knockback damage), and SB dealing x3 and 1/3 (3d rolled to average 10.5, and barely over 1 result damage). If you include the "knockback safety" rule (which I do: each hex of knockback = -1 damage, and knockback based on ST-3 rather than ST-2), FS usually deals 1 point of damage, and SB rarely deals any damage at all! If you treat Shotgun damage the same way, you may get that 1d+1 or +2 of regular damage, and some multiplier for knockback damage (averaging, say, 18-22 points for purposes of knockback, making your average person go back 2-3 yards with the single hit), which brings it MUCH more in-line with the other firearms listed in terms of effectiveness (and that much more realistic, too!)

remember, I'm estimating the rules based on what I KNOW I can do!

Re: 'Shotguns have dkb/dbt' - where did that myth (?) come from?
 

Well, the baddie in question may have a rather different reaction if he's crawling through your window at 4 AM, instead of watching you shoot at a wall on a firing range.

Re: 'Shotguns have dkb/dbt' - where did that myth (?) come from?
 

sorry to say, but my roommate's a marine, and he's shot a 9mm into a plastic milk carton and had the bullet bounch off!

Re: 'Shotguns have dkb/dbt' - where did that myth (?) come from?
 

Eh, yes?

I'm hard-pressed to find the relevance here. Do you mean that because implausible things sometimes happen in the real world, there is no point to scientific research?

Re: 'Shotguns have dkb/dbt' - where did that myth (?) come from?
 

Which considering how many people have all ready told you shotguns do not do knock back, makes this a cinematic not realistic in any way rule.

Re: 'Shotguns have dkb/dbt' - where did that myth (?) come from?
 

Talking about injury mostly, not knockback...
The rule about blunt trauma, I don't see why it'd be doubled for a shotgun and nothing else. However, there's a larger chance of getting multiples of ten to do trauma when you hit with lot of pellets. The really close range rules are kind of nasty for a shotgun, I'd need to look, but I think you count all of the pellets as one attack for armor purposes. If not, then damage maybe should be counted as a total for blunt trauma?

100 hits each doing 9 points, on a vest with DR10, would do nothing. 100 hits on a vest with DR10 doing 10 points of damage would do no penetrating damage, but 100 points of blunt trauma damage. Seems to me the difference is very minimal for such huge difference in effect. If counted as a total, the first one would do 90 points BT.

Re: 'Shotguns have dkb/dbt' - where did that myth (?) come from?
 

You multiply .5 x the ROF-multiplier with both damage and DR for each shot fired to get damage for each shot. So the penetrating damage increases (as you hit a lot more often than is to be expected) and theres lots of more blunt trauma. For even more grit, you could also implement some mechanism to determine the range/conditions at which ALL of the bullets (full ROF-multiplier) hit. I guess the blunt trauma the shotgun inflicts doubles, because flexible amor is designed to divert the force of impact from one bullet and fails to do so when a lot of them hit at the same time, because there will probably be some points at which a lot of different bullets apply impact too, no uniform distribution and also because the amor wafts forward and backward when hit and the part the next pellet strikes just might be already moving towards you so there is not much protection from the dispersion. In fact, the amor might rip at that part and the pellet might penetrate.
Yes, it should, the book says , so to be super realistic you would need to count all of them, even between firefights. 100 hits each doing 9 points damage, would thus do 90, 100 hits each doing 10 pts, 100 points of injury.
Sadly it seems to be a little more complicated than I thought, but I should be getting a nice book soon that covers such questions.

Re: 'Shotguns have dkb/dbt' - where did that myth (?) come from?
 

I strongly disagree with the first part, and strongly agree with the second. Punches should have the arm, shoulder and upper part of the torso (and more importantly the abdomen, legs and especially hips), but a whip crack punch will be devestating if the timing of the crack is good, and much faster and less committing than a battering ram. Of course, it takes a lot of practice to find the proper timing for the crack, but well, fighting is a skill after all - may as well practice it well.