small caliber velocity detector

[singularity]

i want to know the fps of some of my homemade airsoft guns, i saw something using 2 pieces of paper and a microphone but that would probabaly slow down the bb alot (at least thats what i thought i might be wrong) is there a simple circuit i could make for some form of optical detector? or is there an easyier way?

[boilingleadbath]

Opticaly: yes.

I'd say the most common way uses a microphone plug to interface a pair of phototransistors to the sound card. We've had threads on this before... try searching for "chronograph" or "homemade chronograph".
(note, I didn't check those)

[Atlantis]

You could always do the math, my pistol says 0.4J.

You could also be lazy and look your gun up on this site, it tells you what the FPS on each gun SHOULD be.

http://www.airsoftatlanta.com/

[singularity]

well i would look my gun up on that site if i had bought it, but i made it myself (my parents dont let me buy wimpy little airsoft guns but i can build a huge and powerful potato cannon, it doesnt make sense) how would i do the math?

[sum_kid]

same wif my mom man. she givs me cigerettes everyday and lets me b homeless for a whole year and wont let me buy a freakin bb gun wif my own money. in my oppinion cigerettes kill more than bb guns right? anyways try using tishue paper for the first peice of paper or sum other thin paper thats still thick enough to make noise. or if by any chance u got a camera with a really fast frames per second u can count how many frames between the shot and do the math

[chosen_way]

the paper and microphone thing works, http://www.seattleairsoft.com/modules/n ... =15&page=0
well atleats it did for me it wont work if your bb gun is to pissy to shoot throught two peices of paper but if it to pissy to do that it isnt worth the time.

[sum_kid]

i did i wihout the firt paper. juss measure from the loudes point in he begining

[Shrimphead]

Words you spelled wrong, sum_kid:
"i" (it)
"wihout" (without)
"firt" (first)
"juss" (just)
"loudes" (loudest)
"he" (the)
"begining" (beginning)

My point is that you should try harder to type correctly so people can understand what you are trying to say. Also use the shift key and proper punctuation.