All about FPS!

[sushila81]

does a pellet from a 1000 fps airgun goes straighter and accurate than a 650 fps one

[aksd]

Firstly, a pellet does'nt fly straight, but in a trajectory (or even an arc )

Accuracy is not dependant only on velocity, but on mainly the shooter, and where hardware is concerned it depends on your barrel, pellet, and overall shooting characteristics of your rifle/pistol

Regarding Velocity.
Remember with increase in velocity theres in increase in muzzle flip and recoil.

Muzzle flip is due to turbulent air being present behind the pellet. In target guns this has been taken care of using Compensators which disperse this air to an extent.

Recoil cannot be avoided and results in loss of accuracy depending on how well you hold your gun etc... Of course this too has been taken care of in target guns.

When velocity increases the time of the pellet spent in the barrel decreases, this is known as lock time, the higher the velocity of the pellet the shorter the lock time, this reduces the importance of "follow through" which is when you hold the gun in position even after the gun is fired.

[shahid]

Yes for Air Rifles faster is better particularly at ranges beyond 30 yards.

less time to deviate downwards due to gravitational pull.

For other rifles too velocity is good to a certain extent but mainly it is more of knock down power ( hydrostatic shock ) that is essential. An absolute wildcat cartridge with over 3,500 fps of velocity is not the only solution. Faster the MV higher the force of deacceleration.

It is not a very simple explaintaion. A combination of factors with bullet weight, shape, powder, calibre, distance, even weight of rifle everything contributes to accurate grouping.

Similarly for air rifles, match versions may have lower velocity but better balance, recoil, trigger control etc. for perfect groups at 10 m.

Field use air rifles if they group to 1/2 inch at 30 yards are the best one can have. A shooter with practise and good technique will be able to manage that with a modern Diana or HW rifle.

[Sid_kapur30]

How does one calculate the fps of an air rifle ???? and what pellets seem to give a better fps?

Cheers
Sid

[Mack The Knife]

You check the velocity with the use of a chronograph.

Lighter pellets, provided they are not a very tight fit, are faster than heavier pellets.

[mundaire]

FPS or feet per second is a measure of velocity, so you don't calculate the velocity - you measure it!

What you are probably referring to is the velocity of the pellet when it exits the barrel aka "muzzle velocity" (MV). The pellet looses it's velocity as it covers distance, so the MV may be X fps but after (say about) 25 meters it would have fallen to Y fps. Once you have measured the MV, you can calculate the "muzzle energy" (ME) using the weight of the pellet and the measured MV.

To measure the MV you will need a device called a "chronograph".

For more info check out this article by Tom Gaylord -

Airgun formulas and other neat stuff - How to calculate foot-pounds and velocity

For more on how different pellets can affect ME see the following article by BB Pelletier on the PyramydAir blog -

More on muzzle velocity and energy

HTH

Cheers!
Abhijeet

[Sid_kapur30]

thanks
and i'll keep the calculating thing in mind

Cheers
Sid

[art_collector]

Missed you sssoooooooooo much......disnt see any post for so many days wondered if you were away.

One usually loves reading posts of the regular members and you happen to be one of them. Where have you been? Hope you had a wonderful Diwali.


AC

[Sid_kapur30]

Missed you sssoooooooooo much......disnt see any post for so many days wondered if you were away.

One usually loves reading posts of the regular members and you happen to be one of them. Where have you been? Hope you had a wonderful Diwali.


AC

there are some days when one likes to read rather than put something down on the forums; was kind of having those days plus ruined my comp. at home so no more late night games/blogs


and Mack The Knife at what distance do you calculate the FPS for i doubt if i can ever click so fast ???(considering its at 10 meters)

Thanks
Sid

[art_collector]

Well u were missed buddy

AC

[Mack The Knife]

and Mack The Knife at what distance do you calculate the FPS for i doubt if i can ever click so fast ???(considering its at 10 meters)

You can calculate it at the muzzle or any distance you like down range, provided you put the shot past the sensors and don't miss or hit the chrono.

You do not have to click anything. A chrono has two sets of sensors the distance between which is known. The time taken by the projectile to trip / go past both sensors is automatically recorded by the chrono. Since the distance between the sensors is known, the chrono can now work out the velocity of the projectile.

[Sid_kapur30]

Well u were missed buddy

AC

well it's nice to hear that.

Hey Mack The Knife do you guys own the Chronograph with the sensors and all or are there any places where you ae likely to find such chronographs

Dev i believe you checked the F.P.S. of your IHP 35 sometime back, so how did you check it, where did you go / from where did you manage to arrange for the chronograph ???

Cheers
Sid

[Mack The Knife]

I have a chrono. You could import one if you like. It is not a restricted item as far as I know.

[dev]

Dev i believe you checked the F.P.S. of your IHP 35 sometime back, so how did you check it, where did you go / from where did you manage to arrange for the chronograph ???

Cheers
Sid
[/quote]

I used a calculator you get online, its available if you request a chap at the yellowforum.com . I was trying to attach it in my post but it is not allowed because of some complicated html reasons that I won't get in this lifetime. Basically you shoot a close group say ten m and then a far group say 20m and then feed in the pellets ballistic coefficient. The program then calculates the m.v at fps. I am planning on getting a chrony if I can.

Regards,

Dev

[Sid_kapur30]

Ah seems quite complicated (pellets coefficient ????) i think i'll settele with the fact that my rifle now shoots and that too STRAIGHT

Cheers
Sid