chrono'ing an air rifle

[BeerHunter]

Hi

I recently got a secondhand Gamo CF-20 underlever (in .177, unless they all are??).

Anywho, I was wanting to find out what poundage it's shooting at. Is it possible for this to be calculated by me, or do I need to take it to a smith for them to measure?

Thanks

 

[Allybally]

You can take it to any air rifle club, they should do it for free or buy a Chrono for about £50 off the evil web...

Ally

 

[HillBill]

You need a chrono to measure the velocity of the pellet. Once you have your average feet per second you then...

Fps x fps x pellet weight (in grains) divided by 450240

 

[BeerHunter]

Blimey, you lot don't hang about!

many thanks for the speedy replies.

 

[resnikov]

Just to make you aware, if you take it to a gun shop and they test it and it's over the legal limit they might take it off you unless you have a section 1 firearms certificate but if it's over the legal limit and you get stopped by the police then that's a whole world of trouble. So best getting it checked.

 

[ledders666]

You need a chrono to measure the velocity of the pellet. Once you have your average feet per second you then...

Fps x fps x pellet weight (in grains) divided by 450240

Complex way,

most chronos will just tell you the ft/lbs, under 12 is legal over 12 requires FAC simple

http://www.ebay.co.uk/itm/New-COMBR...ograph-Chronoscope-Power-Ft-lbs-/230845009472

I have one of these very easy to use, or as said most gun shops or clubs will check, possibly for a small fee..

 

[Graveworm]

In the time when god was a boy I remember I used to try to work this out with a thimble wrapped in plasticine some scales and a brake cable. No wonder the other kids used to beat me so often.

 

[Big Si]

Or to test in the old days we would shoot it at a metal dustbin and if it when straight through then it was powerfull.:wow1:

Si

 

[Dave]

If you've got an android phone, there are a number of free chrono apps you can download.

 

[Roy]

I recently had my old webley eclipse .22 underlever tested and was surprised that it was still coming in @ 11.6 ft/lbs.
Although it has had little use over the last couple years, it must have been pretty close to the limit when I had a new spring fitted four or five years ago!

 

[Spikey DaPikey]

When I took my new to me rifle to the local gun shop and asked them to check it, it was free, but they also said if it was over the 12ft/lb, they would have to keep it there, but they would offer to detune it to legal levels for about £20, including a full check over at the same time. It's worth getting it done just to make sure you don't run foul of the law. As it was, mine was 11.4ft/lbs

 

[Andy BB]

Many of the rifles in the past were designed to be knocking on the door of 12ft/lbs. Nowadays manufacturers are more cautious and aim for 11.2-11.4 as the norm.

One of the reasons is that different pellets will give significantly different results, and with some of the newer pellet designs, it was taking the standard rifles (and pistols with their 6ft/lb limit) over the limit. So be aware that it doesn't matter what your rifle registers on its normal pellet-fodder, the police can test with a variety of pllets, and if one is over, the gun is illegal. And you are in serious trouble................