How accurate is your chronograph?

[Airgun-Revisions]

A chronograph Is a device that measures speed. Most all measuring devices or tools can be checked or calibrated in some way by using what’s called a standard that’s traceable to NIST
(The National Institute of Standards and Technology)
My question is how do YOU know if your chronograph is actually functioning accurately? Do you even know if it’s accurate when it’s new? How do you check your chronograph to make sure it’s accurately reading true?

 

[JimD]

The only thing I do is compare chronographs. I don't often compare them but I have. My inexpensive Chinese chronographs used to be a few fps different from each other but I shot one of them and I think the replacement compares better but I would have to do a more controlled comparison to be sure.

Whether they are absolutely accurate is not terribly important to me. I normally use them to tune my guns. I want to know if turning the hammer spring adjustment screw gave me more or less velocity. Or how much more or less velocity did I get from a regulator adjustment. The only thing I do with their values where the accuracy of the velocity is important is setting up a trajectory table in Chairgun (or your favorite trajectory program). I shoot at various distances and normally have to juggle the velocity and/or ballistic coefficient and/or height of the scope above the barrel to match my shooting results. My measurement on the bore centerline seems like it should be better but sometimes it helps me get agreement to change it a little. I have no idea what the bc is in my gun. I use the manufacturers published data or data from Hard air magazine. Both are, I assume, measurements of what they got from their gun. Doesn't mean my gun stabilizes them the same.

If the only place you need a really accurate velocity value is in a program where some of the other inputs are not terribly certain why is the velocity value terribly important? Maybe there is a use where that is not the case but for me I don't think absolutely accurate velocity is really necessary. My little inexpensive chronographs give me what I need.

 

[Struckat]

$30 China device, measures in meters. It may be close based on anecdotal evidence.

Use it as directional information. I know what my baselines are for the guns I have, and I only have the one “instrument.”
If the actual numbers differ, it doesn’t matter in my world.

 

[Treefrog]

+/-.25% is what the box says. That's 2.5-fps per thousand. More than good enough for guns that shoot at less than 600-fps. I'm just not OCD enough to worry much about it.

Cheers,

J~

 

[Tumblinginflight]

I’m in lockstep with JimD and his approach. If multiple units read within a few fps of each other it adds some degree of confidence, but at the end of the day the velocity just needs to be in the ballpark. Real data and ballistic truing are tied to results on paper.

 

[Airgun-Revisions]

I’m in lockstep with JimD and his approach. If multiple units read within a few fps of each other it adds some degree of confidence, but at the end of the day the velocity just needs to be in the ballpark. Real data and ballistic truing are tied to results on paper.

For all the people that do not have multiple chronographs which is quite a lot, how did they know that they’re in the ballpark?

 

[Struckat]

For all the people that do not have multiple chronographs which is quite a lot, how did they know that they’re in the ballpark?

I’ll use my 177 HW95 as an example. With FTT most report that they a shooting 880ish or so.
With 3 coils clipped off the spring the China device says 860. I am goo with that.

My AA500 shoots 18 gr @ 910 or so. Also consistent with what I see reported on the forms.

I feel comfortable with the numbers it’s giving me. This my second one. The on off switch stuck in the depressed state on the first one after a year or so. The second one reads exactly the same as the first one.

And I am converting mps to fps, so there is + or - 3 on each reported number. It’s all close enough for my plink and pest shooting.

When there is a problem, a quick check with the device confirms.

 

[Airgun-Revisions]

Here’s another very good question that’s never talked about. I just brought up the reality that chronographs are not tested truly. Now throw in the variables of temperature, altitude and humidity for the gun. When somebody does a review on a gun or a customer purchases a gun from a retailer then shoots it over their chronograph and getting mixed results should they blame the gun for not performing to their chronograph readings and practices?
I’m totally in line with JD’s answer to this so far. And with that being said why are soooo many people so anal about their chronograph readings?

 

[PasadenaMike]

don’t know but as long as it shows consistency and the pellet goes “whack” on a squirrels face it’s good enough. I have the fx chronograph

 

[Vana2]

Have a Beta Chrony, the FX Pocket Radar and a LabRadar and they are all close to the same reading - close enough that the position of the unit (in front, under the barrel, beside the muzzle) could account for the difference.

I don't worry about the chronograph reading anymore than worrying that the guages on my PCPs aren't exact. I record my baselines and do my tuning per my equipment. Though I do note which chronograph I got the velocities from. Figure that the numbers are relatively to my setups and that's good enough for me.

Cheers!

 

[Richely]

I don’t particularly care if it is ‘accurate’, I just want it consistent. Like others I use a chrony to measure performance of a particular gun over time or in response to changes I’ve made. Accuracy compared to some absolute standard is irrelevant.

Why are some so anal about chrony accuracy? Some are just anal, period. Others are anal about things they don’t fully understand. For a few it may really matter, but for most of us it’s whether there is a change from before.

To the point of dealer/manufacture results, differences in pellets, temperature, etc. must be considered over chrony differences. When I received my FWB Sport from AoA it wasn’t shooting anywhere near the fps/fpe their chrony test showed Why? Didn’t for a minute suspect my chrony. It was 40°+ colder here in Minnesota than in Arizona. When temperatures finally were up near their then temperatures my chrony results were in ballpark with theirs. Close enough.

 

[Treefrog]

When somebody does a review on a gun or a customer purchases a gun from a retailer then shoots it over their chronograph and getting mixed results should they blame the gun for not performing to their chronograph readings and practices?

The American way seems to be to emphasize power, and people are unhappy if they believe that they aren't getting the power that they paid for. "There's no replacement for displacement" is commonly believed. That said, there are so many variables when it comes to making parts for and assembling an airgun that there will be a certain amount of variation in the results. The same applies to chronographs, although to a much lesser extent. (I truly wish my guns were as consistent and accurate as my Caldwell is!)

When you add the above to the lack of understanding that many bring to the table, entertainment ensues. People get angry when they don't believe that they're getting the horsepower that was advertised. Can you imagine what it would be like if everyone could put their new ride on a dynamometer when they got it home? Many people would be P.O.'d and K&N sales would go up.

It's wonderful that the chrono has become available to us commoners. An objective standard is critical when it comes to really knowing what is going on with projectiles once they leave our custody.

As Richely said above, some people are just anal about things and they serve to provide entertainment for the rest of us.

I recall being a little sad when the QB78 didn't shoot at the velocity advertised, but took it as a challenge to be met instead of disatisfaction to be expressed. Armed with that knowledge, the journey to the level of performance desired was a lot of fun. The fact that I understood the relationship that temperature and Co2 have at the start was a bonus.

Cheers,

J~

 

[KatoKevin454]

it seems that the chrony is within the same parameters of the Scopes Ballistic calculator, since it hits the target accurately, I would say it is Correct.

 

[Tumblinginflight]

For all the people that do not have multiple chronographs which is quite a lot, how did they know that they’re in the ballpark?

Fair point. While many may not own multiple chronographs, I would think many of those do at least have access to multiple units by way of a friend, family member, random guy at the range, or some ranges even offer them as rentals. At least they could correlate it once, establish a proof gun so to speak.

For someone truly working on their own, it would be tougher, but would come down to a combination of experience and common sense. Understanding what a velocity range “should” be based on manufacturer specs and actual user data would be a reasonable starting point. For troubleshooting a problem gun, or something old, obsolete, a real mystery, I guess it would just come down to faith in the device.

 

[rcarlisle]

I feel mine is accurate enough if I can plug my velocity and pellet into Chairgun, fire a few rounds and see if reality matches what Chairgun says it should be. My Beta unit seems pretty spot on.

 

[Gramps]

A chronograph Is a device that measures speed. Most all measuring devices or tools can be checked or calibrated in some way by using what’s called a standard that’s traceable to NIST
(The National Institute of Standards and Technology)
My question is how do YOU know if your chronograph is actually functioning accurately? Do you even know if it’s accurate when it’s new? How do you check your chronograph to make sure it’s accurately reading true?

I don’t think there is any way the average consumer could check to see if his chrono accurate. The only way would be to compare 2 or more chronographs but you still don’t know which one is correct. The best way would be to shoot the same projectile across 2 chronographs at the same time. If the results are within 5-10 fps I’d say all is good. I checked my $30 Chinese one against my ProChrono DLX & was within 5-10 fps so both were accurate enough for my needs.

 

[crowski]

I had 4 cronies at the same time. They were all very close as far as fps.
The Cadwell and another similar made in Canada, you had to shoot though rings and the lighting had to be perfect. Didn’t like either. Success rate was very low. had the FX as well, pocket. Didn’t like the elastics. Ate batteries.
Got the new FX table model. Absolute gem I can shoot up my targets like regular and it reads everything. I believe the Garmin is just as good if not better. Crow

 

[maxtrouble]

I have a Caldwell and an FX gen 1 chronograph. I feel like the Caldwell is more accurate because it and the rifle half to be perfectly setup every reading.

The FX gen 1 is more convenient and fits in my range bag. It will eat lithium batteries like candy so you have to take them out after every use. The speeds are about 5 or 10 fps below the caldwell but I think this is due to my inconsistencies, not the device itself.

I am really concerned with consistency and the standard deviation of the shot string, not so much the speed. If the manufacturer says 900 fps and I am at 850, no big deal, as long as it is always close to 850.

 

[beerthief]

The American way seems to be to emphasize power, and people are unhappy if they believe that they aren't getting the power that they paid for. "There's no replacement for displacement" is commonly believed. That said, there are so many variables when it comes to making parts for and assembling an airgun that there will be a certain amount of variation in the results. The same applies to chronographs, although to a much lesser extent. (I truly wish my guns were as consistent and accurate as my Caldwell is!)

When you add the above to the lack of understanding that many bring to the table, entertainment ensues. People get angry when they don't believe that they're getting the horsepower that was advertised. Can you imagine what it would be like if everyone could put their new ride on a dynamometer when they got it home? Many people would be P.O.'d and K&N sales would go up.

It's wonderful that the chrono has become available to us commoners. An objective standard is critical when it comes to really knowing what is going on with projectiles once they leave our custody.

As Richely said above, some people are just anal about things and they serve to provide entertainment for the rest of us.

I recall being a little sad when the QB78 didn't shoot at the velocity advertised, but took it as a challenge to be met instead of disatisfaction to be expressed. Armed with that knowledge, the journey to the level of performance desired was a lot of fun. The fact that I understood the relationship that temperature and Co2 have at the start was a bonus.

Cheers,

J~

nicely stated .

 

[Trucker3573]

The American way seems to be to emphasize power, and people are unhappy if they believe that they aren't getting the power that they paid for. "There's no replacement for displacement" is commonly believed. That said, there are so many variables when it comes to making parts for and assembling an airgun that there will be a certain amount of variation in the results. The same applies to chronographs, although to a much lesser extent. (I truly wish my guns were as consistent and accurate as my Caldwell is!)

When you add the above to the lack of understanding that many bring to the table, entertainment ensues. People get angry when they don't believe that they're getting the horsepower that was advertised. Can you imagine what it would be like if everyone could put their new ride on a dynamometer when they got it home? Many people would be P.O.'d and K&N sales would go up.

It's wonderful that the chrono has become available to us commoners. An objective standard is critical when it comes to really knowing what is going on with projectiles once they leave our custody.

As Richely said above, some people are just anal about things and they serve to provide entertainment for the rest of us.

I recall being a little sad when the QB78 didn't shoot at the velocity advertised, but took it as a challenge to be met instead of disatisfaction to be expressed. Armed with that knowledge, the journey to the level of performance desired was a lot of fun. The fact that I understood the relationship that temperature and Co2 have at the start was a bonus.

Cheers,

J~

Exactly….this is very true in the archery industry as well. Compound bows often end up short of manufacturer speed ratings and people will go nuts to find even 5-10 fps more speed.