F1 Chrony test

[Gerard c.]

Now the cometa300 is repaired- new Spring guide and standard spring, what is the procedure to test rifle to see what its output is to make sure all is well? fired a shot over chrony returned reading of around 580 with diablo field heavy (18 grain)

[Phil Russell]

Your figures equate to 13.45 ft lb .. so you are over the UK limit and need to turn the rifle down a tad.

If you added any preload then try removing it. If not the removing a coil may well do the job.
There are many energy calculators on the web if your chono does not give that reading. All you need are pellet wt in grains and muzzle velocity.

The actual equation used is:
E in ftlb = pellet wt in grains x velocity in fps x velocity in fps all divided by 450240

Some equations use a divider of 450435, it all depends on which gravitational constant is used. Convention for air guns seems to be 450240.
Cheers, Phil

[Doxbox]

Extorians ballistic calculator is still lurking about I believe.- - http://extorian.co.uk/shooting/pellets.htm
Very handy little page. If the link doesn't work just google Extorian

[angrybear]

Now the cometa300 is repaired- new Spring guide and standard spring, what is the procedure to test rifle to see what its output is to make sure all is well? fired a shot over chrony returned reading of around 580 with diablo field heavy (18 grain)

in your case 580 x 580 x 18 = 6055200,
6055200/450240 = 13.448
rounded up 13.5ftlb which is obviously well over the 12ftlb UK limit

[lensman57]

Now the cometa300 is repaired- new Spring guide and standard spring, what is the procedure to test rifle to see what its output is to make sure all is well? fired a shot over chrony returned reading of around 580 with diablo field heavy (18 grain)

Get the rifle checked out on another Chrono. I don't trust the readings from my Chrony.

A.G

[Gerard c.]

Thanks for imput, one question the cometa only has the exact parts as fitted when made is it possible the rifle will settle down at all say after 500 pellets,I will see about trying out on another chrono.

[p.sharp]

More than likely settle down at 14.5ftlb if you decided to ‘shoot it in’ 🙂 lopping a few coils off until it sits around mid 10’s is probably the best course of action. Obviously you’d need need to set the power with a pellet that delivers the highest energy reading, which possibly won’t be the 18gr ones you’re testing with currently 🙂

[Phil Russell]

As above really. I cannot see it settling down to below 12...
The fact that you have fitted a 'standard spring' and it is over the limit is, well, not too unusual.
I would take one coil off to start with ... if the spring has a finished end where the end coil is flattened then I would remove this end coil and then flatten/refinish the new end. If this is not enough ... say it gives you hovering on 12 ... then I would simply compress the new end coil and try that before lopping more off. Slowly slowly is the trick.
Cheers, Phil

[rancidtom]

18 grain pellets are way too heavy for most springers to be efficient and I think they may be causing the gun to diesel which can be seriously upsetting the results.
I would also suggest getting a new battery for the chrono (they can give some odd readings when getting low, especially in cold weather, chrono's like to be at room temp and so do batteries, but using an F1 indoors you will have to be careful of the lighting, energy saving bulbs and flourescent tubes are definitely not good. LED or incandescent bulbs such as halogen work if you can't use daylight.)
Lighter pellets such as RWS Hobby, Falcon Accuracy Plus (JSB Jumbo Exact RS) are often the most efficient with this type of gun, if your gun is sub12 with these then it is probably legal with all other pellets, but don't take that as gospel, you have to try a good few to be certain. Every gun is different and that can mean it might be most powerful with a different pellet, possibly Webley Mosquito (JSB Jumbo Exact Express).

[bighit]

Extorians ballistic calculator is still lurking about I believe.- - http://extorian.co.uk/shooting/pellets.htm
Very handy little page. If the link doesn't work just google Extorian

http://extorian.co.uk/shooting/pellets.htm

[Gerard c.]

The Battery has been in the Chrono at least 6 months, so I will change it and try again with RWS hobby pellets Jsb exact and a few others see what happens might even have some pointy spitfires somewhere i was given

[lensman57]

in your case 580 x 580 x 18 = 6055200,
6055200/450240 = 13.448
rounded up 13.5ftlb which is obviously well over the 12ftlb UK limit

I forgot to mention that before any chopping and changing get a tin of JSB Jumbo Express or even Falcon .Accuracy Plus or JSB RS and let the gun settle and then test it with these lighter pellets. Springers usually make more power with the lighter pellets but because of the lower ' starting pressure ' they might also avoid building up the pressure and temprature to a degree to cause auto ingnition of any lubes left over in the compression tube. Does the gun smell of burning oil when fired with the JSB Heavies? Does it smoke?

A.G

[Gerard c.]

lensman, yes you do get a whiff of burning

[lensman57]

lensman, yes you do get a whiff of burning

There is a chance that the gun is ' dieseling '. If you could dismantle and clean up the comp tube, piston, seal and the spring properly and then relube properly ' sparingly ' the problem might go away.

A.G