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I've recently bought a chronograph and have put some shotgun cartridges over it. They were all fibre wad and apart from being a bit slower than expected they seemed to set the chronno off ok. I remember someone on here saying fibre cartridges were hard to chronograph. Why's that?

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47 minutes ago, Wasabi said:

It's an alpha chronny. Nothing fancy but seems accurate when compared to a friends expensive Oeler (spelling?).

It registers fibre wads fine if you back up 5 or so feet. 

he tried different distances, chokes etc to no avail.  light/cloud conditions were the only thing that made a difference I seem to remember!

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3 hours ago, Wasabi said:

What adjustments do you make?

so, here it goes: this is the result of 3 different chrony and 100s of comparative tests between the chrony and the manometric barrel (even in combination). With due adjustments the results have shown  accuracy (95%) and consistency (98%); with less adjustments, the performances  lowers a bit, yet to an acceptable level (90% & 85% respectively). In this conditions we can make safe assumptions on the standard variation which will then give us the final results: to any readings you must add 15-20 m/s (49.2 - 65.6 ft/s)

We know the chrony works with 2 photocel so, amongst the many factor that can inifluence the reading, ligth is the most influent.  We also know that photocels reading is inversely proportional to the light it's exposed to (less light more speed, more light less speed). Therefore, consistent light is paramount for consistent readings the best natural condition is a light but flat cloudy day (so, white thin clouds): light condistions will remain consistent throughout giving you a good base.

Distance is also a key factor in the readings: too close and the gases will distort or invalidate the readings ... or (sadly) break an unprotected screen...; too far and you will be reading a non-standard speed as well as invalidating the assumption we will make.  Therfore the first photocel must be 2 - 2.5 mt from the muzzle to be able to read the V1 (speed at 1 mt) - and save the screen (first time i tried at 30" and it didn't last much)

if we then add the standard variation to the resulting readins we will get the V0 (speed at muzzle)

A fixed shotgun mount with minimal play is also important when aligned with the photocels

so, essentially: 1 photocell at 2-2.5 mt and test done on a cloudy day + standard variation will give you the most accurate readings. 

 If you want to exagerate (i did) you can built a box/shed around the chrony and provide artificial light ( 2x 12V di 30 Watt will do nicely) and plug the chrony to the main for the most consistent results; it will also add an extra layer of  safety for the chrony's screen (whatever you do, protect the screen! it is a ****** breaking it at the beginning of a day testing with 10s of shells to try LOL)

hope it helps.

 

 

 

if you want 90% accuracy you should build a 

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12 hours ago, Continental Shooter said:

so, here it goes: this is the result of 3 different chrony and 100s of comparative tests between the chrony and the manometric barrel (even in combination). With due adjustments the results have shown  accuracy (95%) and consistency (98%); with less adjustments, the performances  lowers a bit, yet to an acceptable level (90% & 85% respectively). In this conditions we can make safe assumptions on the standard variation which will then give us the final results: to any readings you must add 15-20 m/s (49.2 - 65.6 ft/s)

We know the chrony works with 2 photocel so, amongst the many factor that can inifluence the reading, ligth is the most influent.  We also know that photocels reading is inversely proportional to the light it's exposed to (less light more speed, more light less speed). Therefore, consistent light is paramount for consistent readings the best natural condition is a light but flat cloudy day (so, white thin clouds): light condistions will remain consistent throughout giving you a good base.

Distance is also a key factor in the readings: too close and the gases will distort or invalidate the readings ... or (sadly) break an unprotected screen...; too far and you will be reading a non-standard speed as well as invalidating the assumption we will make.  Therfore the first photocel must be 2 - 2.5 mt from the muzzle to be able to read the V1 (speed at 1 mt) - and save the screen (first time i tried at 30" and it didn't last much)

if we then add the standard variation to the resulting readins we will get the V0 (speed at muzzle)

A fixed shotgun mount with minimal play is also important when aligned with the photocels

so, essentially: 1 photocell at 2-2.5 mt and test done on a cloudy day + standard variation will give you the most accurate readings. 

 If you want to exagerate (i did) you can built a box/shed around the chrony and provide artificial light ( 2x 12V di 30 Watt will do nicely) and plug the chrony to the main for the most consistent results; it will also add an extra layer of  safety for the chrony's screen (whatever you do, protect the screen! it is a ****** breaking it at the beginning of a day testing with 10s of shells to try LOL)

hope it helps.

 

 

 

if you want 90% accuracy you should build a 

Does this also apply to fibre wads?

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3 hours ago, Smokersmith said:

Does this also apply to fibre wads?

For that I didn't do enough testing to proof the standard variable, sorry. That said the data I have shows the theory is valid although the accuracy of the readings is slightly below what I'd be comfortable with when giving advise. I'd personally still take the good readings as valid

56 minutes ago, steve s×s said:

How ever did we manage to shoot anything in the past without all this carp (cell phones, cronos, nightvison, Beam me up Scotty)rant over.

It's not a matter of shooting i.e. pulling the trigger and hearing a bang, if that's what matters then I shot coarse salt and pepper in grains... What other people are interested in is how what they're shooting performs...it might not be everyone's cup of tea but I don't see nothing wrong with it. Beaides, if it's not of interest what's the value in reading it and comment on it?

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4 hours ago, Continental Shooter said:

For that I didn't do enough testing to proof the standard variable, sorry. That said the data I have shows the theory is valid although the accuracy of the readings is slightly below what I'd be comfortable with when giving advise. I'd personally still take the good readings as valid

It's not a matter of shooting i.e. pulling the trigger and hearing a bang, if that's what matters then I shot coarse salt and pepper in grains... What other people are interested in is how what they're shooting performs...it might not be everyone's cup of tea but I don't see nothing wrong with it. Beaides, if it's not of interest what's the value in reading it and comment on it?

HaHa the wright fly in the wright place and u will get a take 

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