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.