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Registered Member #193
Joined: Fri Feb 17 2006, 07:04AM
Location: sheffield
Posts: 1022
One of the easiest ways to get an idea of the muzle velocity is to measure the range. The maths isn't that difficult and, while air resistance screws it up, it screws it in the right direction. If you have a range of x it puts a lower bound on the velocity.
Seems to me that measuring velocities, such as what comes out of a spudgun, would be easiest to measure using a high sampling rate computer sound card. Place the microphone half way between the muzzle and the target. The sound spikes in the wave will give you the time interval, and coupled with the measurement of distance will give you a fairly accurate velocity reading.
I've built a few airsoft guns using a pill bottle, Bic pens, and a lighter. Estimating on a cold day, the best one does around 700fps (mach .6-ish) with a .20g bb, which will break beer bottles and penetrate over 4 pop cans. I'm currently working on a smaller, yet more powerful hybrid style airsoft launcher using all metal parts brazed together and an adjustable burst valve to non-lethalize the shots.
Registered Member #659
Joined: Fri Apr 20 2007, 09:14AM
Location: SW Hertfordshire, UK
Posts: 75
I've tried the sound recording technique, but it does have the disadvantage that this thing is quite loud (don't worry about the neighbours, I've explained it to all of them), so the muzzle blast gets mixed up with the sound of impact.
I've tried the sound recording technique, but it does have the disadvantage that this thing is quite loud (don't worry about the neighbours, I've explained it to all of them), so the muzzle blast gets mixed up with the sound of impact.
You can use two microphones R/L, having one by the target and another by the muzzle.
Also have you thought about using a small suppressor or muffler? I built a basic slide on suppressor for the airsoft gun and it quiets the shots enough to not be recognized at 50 feet away. Having a 200+ foot effective range it's quite the special ops piece.
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