Home-Made Chronograph Guide!!!

[DMitri]

Excellent follow through.

I suggest editing your original post.

[DTas2]

Not only did i just find a amazing new AS site but i did the test and there are very similar to when i had my guns professionally chronographed.

My pistol came in at 258FPS and Professional Chronograph said 263 2 months ago.
My shot gun came in a 388FPS and Professional Chronograph said 394 2 months ago

Mind you with as often as I play I think that those few FPS could be from normal wear.

[Mobius]

Ive used this guide to chrono my guns and the next day I chronoed them at OP Mad Dog and teh overall average was the same. this is a great way of chronoing your guns

Props for the find

[Raging Hormann]

If you use physics you can find the amount of drag on a BB: first find the time it takes to go five feet. then find the theoretical time to go 15 feet. the you can find the difference in theoretical vs experimental and then you do some other stuff which I can't remember at this time. but you end up finding the amount of drag and that will help you find out how much it slows down at different distances. Basically all of the chrono and slowing down stuff from a scientific point of view.

[Carpet]

If you really felt like it you could count in the speed of sound, which actually makes a more than estimated differance in your final velocity.

[Mobius]

If you really felt like it you could count in the speed of sound, which actually makes a more than estimated differance in your final velocity.

Not true, Since you are placing the microphone at center the speed of sound is negated due to the time for the sound of the shot to reach the microphone and the time it takes for the sound of the hit to travel to the microphone being the same.

[monkman33]

If you really felt like it you could count in the speed of sound, which actually makes a more than estimated differance in your final velocity.

Not true, Since you are placing the microphone at center the speed of sound is negated due to the time for the sound of the shot to reach the microphone and the time it takes for the sound of the hit to travel to the microphone being the same.

True.

I really like the amount of data presented here. I am going to go test my guns and keep track of the results compared to a "real" chrono.

Texhnically, this is a "real" chron too. All you are doing is using a differnt set of equipment to measure velocity. Great job!

[Allen]

so if heavier bbs fire at slower fps do people use at .25g to chronograph at lower fps and then use .2g in the field. it would allow someone shooting at 415-420fps with .2g bbs to chrono under 400 with .25g bbs?

[PanzerFaust]

Good points. The solution we've found is to keep hi-caps loaded with .20's AT the chronograph. People roll through with an empty magwell, slap in the chrono station mag and test with the correct weight bb's. Mags for most major platforms need to be represented at the station for that to really work.

[Mobius]

Ideally thats how it would work however it doesnt always work that way and we rely on your word, you tell us you loaded up .2s and we trust youre telling the truth.

Allthough usually theyll give you a few .2s to chrono with. but every now and then theres someone there that can do the conversion in their head if you insist on firing .25s

[Allen]

ok, sounds good

[andros]

Mau,

Realy nice project. We were just looking today for a low speed chrono and one we are using for paintball doesn't go below 100fps. And this one is realy accurate with quite nice scale.

By the way. I did check my AEG which on "pro" chrono clocks at 354fps and using this solution I had 357fps which is very accurate in my oppinion.

Can you also tell me what what is standard Vo of your AEG when you were testing it at 22.5feet. Mine on 5feet gave me result of 357fps but on 10feet velocity was 289fps. I'm going to make all the calculation tomorrow but just like to duble check.

[Carpet]

If you really felt like it you could count in the speed of sound, which actually makes a more than estimated differance in your final velocity.

Not true, Since you are placing the microphone at center the speed of sound is negated due to the time for the sound of the shot to reach the microphone and the time it takes for the sound of the hit to travel to the microphone being the same.

True.

I really like the amount of data presented here. I am going to go test my guns and keep track of the results compared to a "real" chrono.

Texhnically, this is a "real" chron too. All you are doing is using a differnt set of equipment to measure velocity. Great job!

Yea, missed that point he made about that earlier. Also, I did this for my JG BAR-10, came out to 190fps, so obviosly I did something wrong. Thing I wonder is how exactly do you know which wave is the impcat wave, because the wove shown in audacity is long and pretty even, I dont get waves as sharp as he does. Also in the latest pictures, he has a veery small part of the wave highlighted for time, how did he figure out to select that area?

So I redid it w/ a 5 foot distance, heres the pics, wondering if I did that right...

350 w/ .2

Heres w/ .28 at 290

[ATF_Malicious]

Thanks for this great guide - ran my Drozd BB Machine Gun FPS by this method and it hits right about where I suspected it was. I posted your guide over at our forum for those that have high powered BB guns to use if they wished.

Sound File - http://www.supload.com/sound_confirm.php?get=535276645.wav

Anyway - appreciate the link - I realize we are dealing with two different caliber of guns - but all in all your information helped me determine FPS at home rather than heading down to the paintball shop or buying a chronograph.

-Mal

[ZEUKI]

If you use physics you can find the amount of drag on a BB: first find the time it takes to go five feet. then find the theoretical time to go 15 feet. the you can find the difference in theoretical vs experimental and then you do some other stuff which I can't remember at this time. but you end up finding the amount of drag and that will help you find out how much it slows down at different distances. Basically all of the chrono and slowing down stuff from a scientific point of view.

here is another way to determine the drag on a projectile. Commonly used in reloading and compared to velocity to determine external ballistics for a particular load/bullet.

The formula for calculating the ballistic coefficient stated by wikipedia:

BC= m....=.....p X l
......Cd X A........Cd
where:
BC = ballistic coefficient
M = mass
A = cross-sectional area
Cd = drag coefficient
ρ (rho) = average density
l = body length

Lucky for those of us who are math illiterate the bullet manufacturers do it for us and put it on the box.
(disregard the periods they were used for spacing because I dont know how to write out mathmatical equasions)