Who do I trust?

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PNW1985 said:
I keep hearing good things about the vikka. Makes me want to try.
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It's this one. It went up a little but still not bad

Screenshot_20230126-100435_Chrome.jpg
 
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Bigragu said:
Before you get rid of either of them you should make sure you are shooting like for like in Ammo weight. Yes, that means to sort for weight. I just finished sorting 1500 of the jsb 33.95 MK2 Heavy’s, and weights went from the lightest at 33.5g all the way to the heaviest at 35.0g. I try to target the batches of 33.9-34, the 34.1-34.2, and the 34.3-34.4 as keepers, the rest become plinking Ammo for when friends come over and want to shoot my guns.

With that said, if I go from a 33.9 tin to a new tin batch and shoot a 34.4, that’s easily a 16-20 FPS difference, and that’s even including idiosyncrasies that come with chronographs.
How do you know you weren’t shooting a 33.5g on one shot and a 35g on the next, as an example if using these pellets?

Just food for thought
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I may be wrong but I believe they said they were using both at the same time? But I could be wrong.
 
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The Caldwell could have been interfering with the FX signal, reducing the number of data points for it to curve fit through, to give the muzzle velocity estimate. Remember, a radar does not measure the MV, it measures the velocity down range and uses that to try to work out the velocity of the pellet at the radar, not the muzzle.
 
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I agree with the conclusion in the linked video, you can't really know which, if either, is more accurate. You could try looking at drop over 50 or 100 yards and see which velocity is closer but there is also uncertainty in the ballistic coefficient. But if one matches the prediction of the ballistics program better I would probably declare it the winner. Might not be more accurate but it would be more convenient to use.

I have two of the inexpensive Chinese ones. One is a clamp on and the other is for tripod mounting. They don't agree with each other either. But they are fairly close. I usually use the tripod one because the clamp on affects the POI and I often shoot groups at the same time as I measure velocity. To me, the less expensive units I use have advantages over the much more expensive FX. They do not require you to set a velocity range and they have rechargable batteries. They are also easier to use than my old Shooting Chrony - which got shot once too many times.
 
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Here's what I tell users of the archery ballistics app I wrote..

You can use a chronograph. If you use a chronograph to set your velocity, your sight marks might be close but not exact unless you happen to get lucky. Reason? Chronographs will only give the same readings if they are calibrated to each other. Assume your chrono will be within 3% of the one used to calibrate the program. At 280fps that could be a difference of 8fps. Compare the long marks on 2 tapes made at 280 and 288. Your velocity from two shot in marks will be more accurate when making a sight tape because the velocity calculated from two marks is the velocity of the sight system..taking into account peep height, sight radius, and arrow drag.

Lighting can also have an effect on the resulting velocities you get from the same chronograph. Cloudy VS sunny VS partly cloudy. Your individual chronograph may give different readings based on the light source..especially if it is the type that depends on triggering by a projectile passing over two light sensors.
 
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beerthief said:
should not rest the barrel on anything ever . I set my crony on a tripod and put the barrel close to the clamp but just not touching . Think Barrel Harmonics
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It's not fully rested. I'm holding the slinger. Just use the bottom bracket to line up the barrel with the Chrony so I don't hit the little posts🥴
 
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PNW1985.
You are correct about being frustrated. You paid good money for a ACCURATE device to measure speed. The mfg has only one job.....send the customer a accurate/tested product. The defective product should be returned with empirical evidence that it is defective. This will get your money back.
Whenever I don't trust my chrony, I test with single stroke pneumatics in my collection A FWB 603 10 meter rifle and a Russian pistol. Both of these have a extreme spread of 4 f.p.s. I have also discovered that a fresh battery is sometimes needed to get my chrony to return to perfection.
I also clean shadow sensors with alcohol and then applied 3M packing tape Clear over the sensors to prevent future dust from settling on the sensors. This info is not required of coarse for radar chronies.
I hate rip off products. Glad to see you are telling the truth on them.
 
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Having spent more than twenty years doing sciencey stuff for a living, I generally respect those that set the primary standard for what's being measured. The ASTM was our bible of sorts for various NIOSH testing and analysis protocols. For some reason I always got stuck with the QC lab work... All that said, here's how the gubmint does it. I suppose that a motivated individual could build one for their own use.

www.nist.gov

Reference Ballistic Chronograph

The NIST-developed reference ballistic chronograph (RBC) provides repeatable measurements of the speed of a bullet that will impact a test article, such as p
www.nist.gov www.nist.gov

By the way, did you know that a spitwad fired from a bic pen body travels at about 60-fps?

J~
 
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