Chronograph Best At The Moment

[madcarlos]

I have a Skan chrono, square black box with red led screen which shows a number which you have to calculate the number. You shoot through a 2 inch hole with a paper or card slot so as to not hit the machine and get the pellet in the correct place. Worked very well for years but now i have to re shoot because the machine doesn't recognise a pellet reading, have to do it again. Not sure if the led is dirty with dust or the electronics are failing. It would be good to get this corrected, if anyone knew what to do or which electronic component usually fails.

If my first shot dont calculate I shove a pen through the window, Seems to reset it. I've still got the instructions of mine I'll check to see what it says ,

[BC312]

I have a re set button on the bottom of the box, does yours?

[Ryde]

I have a Chrony Alpha, it's accurate and saves a string of shots etc. so great functions

But it takes a lot of time to set up and I'm always wary about killing it with a misplaced shot. Thankfully the Alpha has the brain on a lead so the front is metal but not very thick.

But I'd like an FX for sure.

[ChrisC]

The LNBR chronos are used in both the FT and HFT comps. I have one for setting up serviced steyrs.

[billywhizz1]

On the cheap chinese ones you need a calculator to change mps -fps. i use a app on my phone called air gun calc. works very well and easy to use.

[Travis299]

On the cheap chinese ones you need a calculator to change mps -fps. i use a app on my phone called air gun calc. works very well and easy to use.

This may help.

FPS = Feet Per Second, MPS = Meters Per Second, FPE = Foot Pounds of Energy
To convert to Joules multiply FPE by 1.3558, Joules to FPE multiply by .7376
To convert MPS to FPS, MPS x 3.2808399 = FPS
To convert FPS to MPS, FPS x .3048 = MPS
FPE Formula is Pellet weight (gr) x FPS x FPS divided by 450240 or 450436.7

[NateChrony]

What’s a more compact and up to date chronograph, not one of those awful things that goes on the muzzle, but something decent that doesn’t cost more than £140 or I won’t buy it.

Do you have an issue with it being muzzle mounted?
or are you referring to a specific make/model?

[NateChrony]

I’ve got an old Skan chronograph that really ought to go to a collector. It’s got red LEDs and a button and it’s black and rectangular like something off a 70s BBC sci-fi like Blake’s 7.
What’s a more compact and up to date chronograph, not one of those awful things that goes on the muzzle, but something decent that doesn’t cost more than £140 or I won’t buy it.
What are all the cool kids measuring their speeds with the now?

Probably need to start with your requirements...
Barrel mounted = cant be shot, can be used in confined spaces, can be less prone to interference
Need BC calculations? then its probably radar
Use safely in tight spaces?
Shot strings?
Interface requirements? Buttons/App...

[Gambo]

FPE Formula is Pellet weight (gr) x FPS x FPS divided by 450240 or 450436.7

I've never heard about dividing by 450436.7 before......can you elaborate please Travis? Thanks.


I have been using a Skan for years, it's been superb.

[angrybear]

I've never heard about dividing by 450436.7 before......can you elaborate please Travis? Thanks.


I have been using a Skan for years, it's been superb.

How about dividing by 450800 ???
this is from the Helston Forensics Standard Airgun test;

[ballisticboy]

How about dividing by 450800 ???
this is from the Helston Forensics Standard Airgun test;

The "formula" at the top of the page is completely wrong, it is 2 x G, not G squared. They have also used an old incorrect value for G. The calculation has used G + G which is not G squared and the way it is written would not give the answer they have if the calculation is carried out in the correct order. Also, grams and grains are measures of mass not weight, so basically whoever wrote that "formula" or carried out the calculation is mathematically ignorant. Unfortunately, only too common of people in the commercial forensic laboratories based on the evidence I saw when working.

The value 450436.7 comes when the internationally correct accepted value for acceleration due to gravity is used.

[Travis299]

I've never heard about dividing by 450436.7 before......can you elaborate please Travis? Thanks.


I have been using a Skan for years, it's been superb.

450240 is 2 x velocity of gravity x 7000, (2 x 32.16 x 7000 = 450240)
450436.7 is 2 x velocity of gravity x 7000, (2 x 32.17405 x 7000 = 450436.7)
The constant 450240 or 450436.7 depends on which value you use for the velocity of gravity.
32.16 ft/s/s or 32.17405 ft/s/s. There are 7000 grains in one pound.
The difference does not matter which ever constant is used for the FPE calculation.

[Gambo]

Thanks for the reply Travis.

[Shed tuner]

450240 is 2 x velocity of gravity x 7000, (2 x 32.16 x 7000 = 450240)
450436.7 is 2 x velocity of gravity x 7000, (2 x 32.17405 x 7000 = 450436.7)
The constant 450240 or 450436.7 depends on which value you use for the velocity of gravity.
32.16 ft/s/s or 32.17405 ft/s/s. There are 7000 grains in one pound.
The difference does not matter which ever constant is used for the FPE calculation.

good info, I'd only ever seen the 450240 figure before.

The difference between that and the 450437 is around 0.04% though, so not really relevant and certainly less significant that a one fps chrono error...

[ballisticboy]

450240 is 2 x velocity of gravity x 7000, (2 x 32.16 x 7000 = 450240)
450436.7 is 2 x velocity of gravity x 7000, (2 x 32.17405 x 7000 = 450436.7)
The constant 450240 or 450436.7 depends on which value you use for the velocity of gravity.
32.16 ft/s/s or 32.17405 ft/s/s. There are 7000 grains in one pound.
The difference does not matter which ever constant is used for the FPE calculation.

It is not a "velocity of gravity" it is the acceleration due to gravity. As I said before, the second value 32.17405 is the ft/s/s value of the internationally accepted value for the acceleration due to gravity, which is actually 9.80665 metres per second squared.