Poor Man's Chronograph?

[TheTrooper]

I remember in airsoft there was a cheap and not always reliable way to figure out your fps with a regular soda can, The Poor Man's Chronograph.
http://www.redwolfairsoft.com/redwolf/a ... ulletID=34
Is there such a thing when it comes to bigger spud guns? Like if you can penetrate 1/4" plywood with a <grams> rock your spud gun can fire <FPS>. Because i would like to test my spud gun, http://www.spudfiles.com/forums/viewtop ... tml#135318
and figure out how powerful it really is. I know there are many variables to take in to question, but i just want a estimate.

[frankrede]

The results are dependent on your ammo.
My golfball cannon at 500fps can go through 1" ply wood, but my marble gun at 500 fps won't

[TheTrooper]

Well i was thinking of a plain rock going through 1/4" plywood(small rock that will fit in 3/4" barrel)

[Zen///]

I posted the poor man's chronoghaph before.... (it was my first post)

And the mods locked the topic and made me sad

[frankrede]

Well i was thinking of a plain rock going through 1/4" plywood(small rock that will fit in 3/4" barrel)

Well rocks can vary with density and shape.
You would have to use a chronograph anyways, to make the chart.
and plywood can vary in composition too.

[JDP12]

i don't think that's a good test- look at all the posts about APFSPS (spelling?) rounds. Thinner rounds will penetrate more than a blunter round, heavier rounds more than a lighter round, denser round more than a less dense round, adn so on and so on, so i don't think that test is good at all

[singularity]

get a mic turn it on when you fire and put it relatively close, it will record a spike when the gun is fired and another when the projectile impacts the target (as long as the mic is sensitive enough) then measure the distance between the two and you can calculate the speed(in fps if you want)

speed = distance/time

you might need two mics one at the barrel of the gun the second at the target, and for the recording app i recommend <a href="http://audacity.sourceforge.net/">audacity</a>

[TheTrooper]

I have everything for the sound test except a laptop, and i don't know anyone who would let me use it for these kinds of tests. Oh well it was worth a shot.