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Thoughts On Homemade Safety

maybe I'm overanalyzing things

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#1 Doom

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Posted 10 December 2008 - 02:36 PM

I was reading some recent comments by VACC that implied that most wars won't accept homemade air guns for safety reasons. I agree that safety should be a concern, but banning air guns for being powerful is very inconsistent with reality.

Edit: For clarification, my main point is that ALL homemade guns have the potential to be unsafe and thus deserve a respect for their capabilities. If you don't read anything else, read that.

Lately I've been doing some computer modeling of a dart's trajectory to help me design a more efficient Nerf gun. My model should be very consistent with reality with given its assumptions are true. No wind and stable darts are the two main assumptions. Drag is taken into account. I can use this model to analyze the ballistics of different Nerf guns.

The PlusBow is a powerful homemade spring gun that hasn't been specifically banned at any wars as far as I know. For those reasons I'll use it as a basis of comparison. Assuming a dart weight of 4 grams, cylindrical shaped darts (which have a coefficient of drag of about 0.82), and a starting height of 4.5 feet, the muzzle velocity would be about 180 ft/s to achieve the advertised maximum range of 140 feet.

With my air pressure FANG Nerf gun the range at 30 PSI was about 115 feet with similar darts. This means the muzzle velocity is about 150 ft/s. Let me note that my range measurement has a somewhat large error because I measured it with strides, so take it to be within 10 feet in either direction.

Some of you might say that the difference is only 30 ft/s. But that still illustrates my point--my air gun is less powerful, but still "too dangerous". I'm hoping to use a combination of more aerodynamic darts and reduced range to reduce my velocity even further while increasing my efficiency, but by under a straight air gun ban those efforts wouldn't matter.

What really matters is kinetic energy density (KED). Hasbro uses this measurement. The PlusBow has a maximum KED of about 2900 ft-lbf/ft^2. The FANG has a maximum KED of about 2000 ft-lbf/ft^2. My air gun has about 2/3 of the kinetic energy of the PlusBow, making it that much safer.

Why banning air guns for being too powerful is inconsistent with reality should be apparent by now. All Nerf guns are capable of being dangerous, especially in irresponsible hands. I'm perfectly fine with banning dangerous Nerf guns. But I'm only fine if the reasons are consistent. If this means all homemade guns should be tested for safety or outright banned at most wars, so be it.

I'll admit that it is easy to test an air gun at one power level and use it in the war at another. But it also isn't difficult to swap springs or use different darts (darts that could be lighter or have more friction during testing).

[ignore]One last rant: I've read on many occasions that Slug darts are safer than other darts. From a maximum KED perspective, this is not true. While there is a little bit of foam on the tip to absorb energy, the energy absorbed by that can't be very large. Compared against something with a coefficient of drag of 0.2, a reasonably achievable number, more than 40% more energy is needed to get the same range with a cylinder shaped dart.

With that being said, I use Slug darts because they're cheap and easy to make consistent. Until an aerodynamic dart with at least the same consistency is possible that is not likely to change.[/ignore]

The parts in the [ignore] tag are nonsense as the higher drag coefficient can be thought of a safety feature at long ranges. I left this is because I do like to note that I'm wrong at times.

Edited by Doom, 19 November 2009 - 09:16 PM.

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#2 UpperHand

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Posted 10 December 2008 - 02:47 PM

Holy shit, thats some pretty deep analysis. The main reason I think that air guns are banned at wars however, is that they don't have overpressure valves, so their users can pump them as much as they want. Sure the air power is only slightly more powerful than a springer at 5 pumps, but what is to stop the user from pumping 10 or 15 more times?
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#3 Doom

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Posted 10 December 2008 - 02:53 PM

If you think that was deep, I actually cut out a part where I started talking about the modulus of resilience because I realized no one would understand what I said.

About safety valves, that's an interesting point, but that only applies to hand pump guns. Adding a safety valve would not be difficult if that was desired.

The other type of gas guns are those with regulated pressure, but they're rare. Their pressure is limited at a certain level that can easily be checked.

Edited by Doom, 10 December 2008 - 02:53 PM.

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#4 VACC

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Posted 10 December 2008 - 02:55 PM

I was reading some recent comments by VACC that suggested that most wars won't accept homemade air guns for safety reasons. I agree that safety should be a concern, but banning air guns for being powerful is very inconsistent with reality.


Nowhere in the post you linked did I mention "safety reasons". Your assumptions concerning the plusbow are also fairly inaccurate.

Seems like you out-thought yourself.
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#5 Doom

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Posted 10 December 2008 - 02:56 PM

Perhaps the word "suggested" was too strong. I'll change it to "implied". If that's not what you mean too, that's fine. It got me thinking.

May I ask why my assumptions concerning the PlusBow are inaccurate too? Has specifically the PlusBow been banned before?

Edited by Doom, 10 December 2008 - 02:58 PM.

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#6 VACC

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Posted 10 December 2008 - 03:13 PM

It seems like the assumptions you've made in this argument are based around the fact that you have a homemade air gun with a potentially smaller range than that reported for a spring based homemade which you do not have. To argue that a gun that does not shoot as far is, generally speaking, not as dangerous is just a statement of the obvious.

I'm sure there are many such guns with lesser range than spring based homemades, or even name brand air guns. If an organizer wants to judge guns on a case by case basis this is relevant. If he does not, it's not.
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#7 Doom

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Posted 10 December 2008 - 03:22 PM

Well, I'm glad you feel that way because I was getting the opposite impression to a certain extent from your earlier post. I think banning anything for simply being something regardless of problems is inconsistent. Perhaps that's my statement (with a bunch of math). Again, it really is up to the organizer, but the attendees also have a say in which wars are successful or not.

Edited by Doom, 10 December 2008 - 03:27 PM.

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#8 VACC

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Posted 10 December 2008 - 03:40 PM

Please don't interpret my comments. I haven't discussed my personal opinion on the matter anywhere in this thread.
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#9 Shrub

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Posted 10 December 2008 - 04:01 PM

Doom this all maybe true, but you have to think that people don't just automaticly know :
You're (generally speaking) telling the truth about ranges, velocity.
VACC raises a good argument about the +Bow.
Just becuase the regular operating PSI I bet you could hold quite a bit more PSI in that tank (generally speaking).

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#10 CaptainSlug

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Posted 10 December 2008 - 04:56 PM

The problem with your assumptions as to why they are usually banned is that.
1. It's extremely rare and difficult to make a springer that shoots to unsafe distances.
2. It's extremely commonplace and easy to make a pneumatic blaster that shoots to unsafe distances.

Assuming a dart weight of 4 grams

Kind of on the heavy side. The ones I make and use (and many others seem to be using now) weigh only 1 gram.
So your KED for my +Bow and darts is off by a large amount.

Edited by CaptainSlug, 10 December 2008 - 04:58 PM.

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#11 Shadowblade

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Posted 10 December 2008 - 05:19 PM

Don't know if this is worth anything, but I am allowing rork to field-test his PixieBlast 9000, a homemade airgun, at Fall SENO. However, I agree with CS on this issue.

Edited by Shadowblade, 10 December 2008 - 05:19 PM.

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#12 rork

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Posted 10 December 2008 - 06:40 PM

I personally believe case-by-case legality, combined with quality homemades, to be the best solution. At any theoretical war that I was hosting, I would ask that anyone who wanted to use a homemade airgun to forward me the specs on it, so it could be evaluated. If it wasn't just another pvc cannon, it could be brought to the war, where it would be tested physically against a pre-set range limit based, say, on the BBBB. A final, more abstract consideration (which would really only be appropriate for smaller events) would be personal qualifications; I believe that it would be entirely appropriate to be a bit lenient (pump limitations and so forth) with people known to be non-douchebags. Douchebaggery would result in being shown the door. A final thought: the kinds of homemades that would be allowed are pretty rare, so I don't see pre-evaluation being a huge issue. Thoughts?
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#13 BustaNinja

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Posted 10 December 2008 - 06:50 PM

War experience here, +bows really can shoot like people say. Doom is fairly accurate. At about 10ft, a +bow can easily pierce a full pop can and go al the way through in one shot. Sound bad? It is. Big Blast can do the same. However, the only reason most guns are banned is because of the general users being butt heads. At MN wars atleast, we (big blast users, and i will fully admit to this) would often shoot at to close of a range. That caused some hard feelings, however, at the same range, a +bow can do just as much. Difference? Ryan doesn't run up that close, nor did Sam. So yeah, spring guns cannot be more dangerous if not more then pump guns, but it all comes down to you. Would you be willing to be shot by it? Any gun I think is over powered that I own, i will offer to have people shoot at me with. I have sense decided that Big Blasts will be banned at any way I host ever, pump plugged or not, as there is too much potential.

So in all that rambling, I guess what Im trying to say is "Yeah, spring guns can be bad, but people are more open to them because they have a set power. You can't over pump a spring gun"
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#14 Doom

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Posted 10 December 2008 - 07:28 PM

Let me reiterate the point I made in my second paragraph because some people seem confused about what exactly I'm arguing for. A flat ban of air guns is inconsistent with reality. I realize it is much easier to make an dangerous air pressure gun than a spring gun, but the problem exists for all homemade guns (and many modified guns). Focus on the actual problem. In this respect I think I agree with most people here.

@VACC: I guess I read into your comments a bit too much. I'll try not to do that.

Just becuase the regular operating PSI I bet you could hold quite a bit more PSI in that tank (generally speaking).


Could you explain what you mean? I don't have a clue.

Kind of on the heavy side. The ones I make and use (and many others seem to be using now) weigh only 1 gram.
So your KED for my +Bow and darts is off by a large amount.


I did estimate the weight and I doubled my estimate to make sure my numbers were closer so no one could accuse me of fixing the numbers to illustrate my point. These numbers were simply for illustration.

1 gram is less than the weight of the washer going by the dimensions and the density of steel. The washer should weigh about 1.06 grams alone, 1.01 for the lightest steel alloys. 2 grams would make sense, but I'd have a hard time believing 1 gram.

My darts were made to your specifications so they should weigh approximately the same.

Redoing the math with 2 grams, the FANG needs a muzzle velocity of about 200 ft/s and has a KED of about 1800 ft-lbf/ft^2. The PlusBow needs a muzzle velocity of about 260 ft/s and has a KED of about 3000 ft-lbf/ft^2. The KED figures are reasonably close to my originals.

I tried 1 gram, but the muzzle velocities required to get decent range were enormous. The PlusBow doesn't shoot darts at 650 ft/s (about Mach 0.6) so I can say with certainty that your darts weigh more than 1 gram. Or my math's incorrect, which I'm checking right now. Actually, my math's definitely incorrect for this particular situation because my drag coefficients are constant, which isn't true over a wide range of velocities but close enough. 650 ft/s is probably low.

Don't know if this is worth anything, but I am allowing rork to field-test his PixieBlast 9000, a homemade airgun, at Fall SENO. However, I agree with CS on this issue.


That's good, because there's no reason for that gun to be deemed unsafe. In fact, I don't think unmodified hose handles are a very efficient valve, unless his hose handle is substantially different from the ones I've toyed with.

I personally believe case-by-case legality, combined with quality homemades, to be the best solution. At any theoretical war that I was hosting, I would ask that anyone who wanted to use a homemade airgun to forward me the specs on it, so it could be evaluated. If it wasn't just another pvc cannon, it could be brought to the war, where it would be tested physically against a pre-set range limit based, say, on the BBBB. A final, more abstract consideration (which would really only be appropriate for smaller events) would be personal qualifications; I believe that it would be entirely appropriate to be a bit lenient (pump limitations and so forth) with people known to be non-douchebags. Douchebaggery would result in being shown the door. A final thought: the kinds of homemades that would be allowed are pretty rare, so I don't see pre-evaluation being a huge issue. Thoughts?


This sounds very reasonable to me. I probably would do something similar if I hosted a war.

Responsibility seems to be very important for safety to begin with, so it would make a lot of sense to ban irresponsible people from using more powerful guns.

To reiterate a point I had made earlier, a simple maximum range wouldn't make much sense. KED is the actual problem. Aerodynamic darts could get high range without high KED. Muzzle velocity and dart weight tests are all that is necessary. Muzzle velocity could be estimated using something like my ballistic model if no measurement device is available.

So in all that rambling, I guess what Im trying to say is "Yeah, spring guns can be bad, but people are more open to them because they have a set power. You can't over pump a spring gun"


This goes back to responsibility. The PlusBow users put a good deal of work into their gun and have a respect for what it is capable of. Generally I'd say willingness to do hard work and responsibility go together. Modifying a Big Blast takes considerably less work so it is much more accessible to the less responsible.

As for the potential for problems with air guns, again, it's not difficult to swap springs or use different darts when testing. Swapping springs definitely can't be done by accident though, so the point is valid, though, with responsible people this will not be an issue. Safety valves and pressure regulators set and locked to a certain pressure help too.

In my opinion, the DBAD rule ("don't be a douchebag") should be primary. If someone with an established reputation for being trustworthy, builds a homemade, any homemade, and they say it will be used responsibly, then the hosts of the event should only need to decide if they feel the blaster is safe overall.

Irresponsible use, however, is always grounds for ejecting any blaster and/or player. And that would include irresponsible use of anything, even as lame as a stock Atom Blaster*."


I agree--you beat me to half the point of my post!
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#15 VACC

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Posted 11 December 2008 - 08:49 AM

At a large war you usually do not know most of the participants personally. Would you judge how responsible they are by the t-shirt they're wearing, or their age alone? Would you only allow the nerfers you do know personally to use potentially overpowered weapons? What equity is there in that? If your war is a small gathering of friends none of this is probably neccesary, but if you are hosting a large war it become impractical to judge and enforce. It's simply easier to create guidlines and enforce them without exception. That said, nerf is in no way a standardized sport, and every event is different (which is half the fun). Each organizer should decide what is best for their war, and the participants should respect that decision, or refrain from attending.

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