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Supersonic Shots.
Are supersonic shots possible with a air gun? Yes, many magnum models have reached the 1,000 fps mark and when oiled can pass speeds of 1,200 fps. When you break the sound barrier a loud sound is heard, much like that of gun powder weapon, this is caused by the pellet breaking the sound barrier. Some call this a supersonic shot or a supersonic crack.
For months me and Steve in NC have been have been discussing the speed of sound, off and on. I had read years ago that the speed of sound was 1,080 fps and I always stated and believed this, Steve disagreed. It seems Steve was right on some points and we both agreed that the speed of sound does vary. After a 2 days discussion with Steve on my air gun forum, I found that that there were other factors that had to taken in account and that the speed of sound varies . One factor that must be taken in account is the temperature, lower temperatures reduce the speed of sound, higher temperatures increase the speed of sound. Another important factor is the altitude where one lives. To break the sound barrier at 1,079 fps, a person would have to do the test at a altitude of 9,600 feet above sea level, at a temperature of 24 F. But if the person is at a altitude of 2,800 feet above sea level, the sound barrier is 1,106 fps, I live more or less at this altitude. At both altitudes breaking the sound barrier with a magnum air gun is possible.
I have chronyed my B-21/Super Max 1000 at speeds over 1,200 fps. Here I have a some chrony notes of some shots that have passed/broken the sound barrier where I live, the sound barrier here is any where from 1,106 fps and up to 1,110 fps depending on the weather: 1125 fps, 1214 fps, 1152 fps, 1248, fps, all these shots were done after treating my B-21 a few drops of Slick 50, on each shot I heard a loud supersonic sound (a ka-pow sound) which sounded like a high powered gun powder weapon. Non of the other lower power spring piston air guns I have chrony tested have given off this supersonic sound after being treated with Slick 50.
Many air gunners believe that the noise is from combustion, I believe the noise is from the pellet breaking the sound barrier. I do agree that there is some combustion and that this combustion might increase the speed of a pellet, but the loud gun shot noise is not from the combustion, it is from the pellet breaking the sound barrier. It is normal for a spring piston air gun to diesel after being oiled, but I do not believe the loud gun shot sound comes from combustion in it's self.
I was taught that in a gun powder weapon it is not the combustion of the gun powder that creates the gun's loud gun shot noise, it is the projectile breaking the sound barrier. This is proven, by using a small hand gun with .22 cal. short bullet , this bullet travels at 750 fps, there is no supersonic sound or Ka pow noise, the small hand gun sounds like a regular air gun, even though there is combustion from the gun powder of the shell. The reason is there is no gun shot sound is that the bullet of the .22 short does not break the sound barrier (over 1,100 fps and up to 1,300 fps). I believe this same rule applies to air guns.
I will give you a simple test, some info and a few links to let you judge for yourself.
Testing for a Super Sonic Shot.
First you must find out what is the altitude where you live, this can be found out by contacting a weather station or looking it up in the internet.
Once you have found out what
your altitude is you may use the following interactive page that gives you the
speed of sound according to the temperature and the altitude where you
live. Click on the drop down list, then click on "sound speed"
first and move the plane to your altitude. This link was sent by
Steve in NC, thank you Steve in NC.
Click below:
http://www.grc.nasa.gov/WWW/K-12/airplane/atmosi.html
Once you have the speed of sound of your area, you will need a Chrony unit that is used to measure the speeds of bullets, arrows, shotgun-pellets, air-gun pellets. This unit of measuring the speed of the pellet will prove that your shot has passed the sound barrier where you live. Of course the noise of the super sonic shot is also a tell tale sound.
There is also more interesting information about the super sonic shot on the internet, click below and look down the page and read "Supersonic Crack". There is a good chart there that helps explain the speeds of a sub-sonic shot, a transonic shot and a supersonic shot. If you study the chart carefully, you will find that sub sonic shots have very little noise even though there is combustion from the gun powder, only the transonic/supersonic have a very loud gun shot noise or as the author says; a supersonic crack, this is measured in sound dB's. Very interesting. Click below.
http://www.guns.connect.fi/gow/highpow.html
You may let me know what decision you have come to on my air gun forum if you like or you may state your own opinion. Look in the index and click on "Eddie's Air Gun Forum".
Well I hope you all find this interesting, I sure do.
Eddie