# COMMUNITY : FORUMS : TECH

## psi and fps??

I am wondering how much fps/ a 300 psi/ is. Iam icelandic and not wery good at english but man when iÂ´m finished making my air rifle youÂ´ll get the best instructable youÂ´ve ever seen!!!

sort by: active | newest | oldest
lemonie10 years ago
There's no direct relationship between psi & fps alone. For your gun there will be a relationship which can be determined, but specific to your gun. One way to measure fps is to fire into a pendulum (of known mass) which will record maximum swing (in degrees). If you know the masses of pendulum and bullet, you can calculate fps from Newtonian mechanics, trig', and other maths (I looked for a link but didn't find one) L
Enzo55 (author)  lemonie10 years ago
WEll okay. Hehe ofcourse. But could you guess on the fps if i give you example of the power?? This thing will put a hole through a 18mm plywood. I would also like your opinion on if that power is enough to kill a geese, duck, rabbit our a fox... 18mm plywood compared to geese. My gun is made out of copper pipe as the barrel and air tank is a ABS pipe. I use a tire inflator air compressor to get to 300psi. Got better ideas?
10 years ago
. If you can put a hole in 3/4" plywood, you should be able to drop a human with just about any projectile near the size/weight of a .22 bullet (or larger). What are you shooting? Takes quite a bit of power to poke a hole in plywood - even with a light .177 steel BB, it should work on varmints/small game.
Enzo55 (author)  NachoMahma10 years ago
Whats a small game? Just give me an example. Is a geese in the "small game" area??
10 years ago
. Mice, squirrels, rabbits, cats, prairie dogs, birds, guinea pigs, fox, etc ... and geese. Not sure what the official definition of "small game" is, but for me it's just about anything under about 40 pounds. . The larger and more massive your projectile, the more knockdown energy it will have.
10 years ago
I think that if you can take out ply' you can take out small game.
This thing isn't rifled though, so you're not going to have a lot of accuracy.
But see if you can get a ballistic pendulum reading.

L
NachoMahma10 years ago
. You may be able to find something on air rifle manufacturers' sites. Crosman (sp?), Benjamin, Daisy, etc.
Bran10 years ago
I do believe that to find the fps as according to a certain psi, you must also know the weight (or the mass) and factor that in. As to how you would do it, I'm not quite sure. I'm guessing you mean the fps when the object first exits the barrel. If you cannot find a way, you could always buy a chronograph, but that might run you a little bit of cash. Good luck with it! Oh, and let me guess - this will be entered in the Launch It! contest, right?