Lets talk chrongraphs
- Thread starter lttuna
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I've never had trouble with my little F1 Chrony. I love it for $80, but that's all the advice I can give you. It's also about the cheapest out there.
all you do is unfold it, turn it on, and then place 8 rods into it and the sunshade on it on sunny days. Then shoot in between the rods. It's so simple--no calibration, no adjusting.
all you do is unfold it, turn it on, and then place 8 rods into it and the sunshade on it on sunny days. Then shoot in between the rods. It's so simple--no calibration, no adjusting.
1911Tuner
Moderator Emeritus
After messin' around with chronographs for years, I've learned a thing or three.
Home chronographs are interesting, and pretty good tools for comparisons, but for determining an absolute velocity...not so much. Too many variables to be that precise.
I've had my chrony give different results with the same ammo lot on different days, despite my being careful to eliminate any and all variables. I've had two identical chronographs give different results with the same ammo lot fired back to back on the same day. I saw two Shooting Cronys lined up in tandem show slightly higher velocities on the second one...when it should have shown lower velocities.
For instance, firing across the eyes or through the screens at the slightest angle will skew the numbers from lot to lot or from shot to shot. A slight change in lighting and even a 10 degree difference in temperature will do the same...as will a change in relative humidity. If the device isn't dead level and square to the gun, you can expect variations.
Enjoy your chronograph, but accept it for what it is. You can drive yourself to drink with one if you don't.
Home chronographs are interesting, and pretty good tools for comparisons, but for determining an absolute velocity...not so much. Too many variables to be that precise.
I've had my chrony give different results with the same ammo lot on different days, despite my being careful to eliminate any and all variables. I've had two identical chronographs give different results with the same ammo lot fired back to back on the same day. I saw two Shooting Cronys lined up in tandem show slightly higher velocities on the second one...when it should have shown lower velocities.
For instance, firing across the eyes or through the screens at the slightest angle will skew the numbers from lot to lot or from shot to shot. A slight change in lighting and even a 10 degree difference in temperature will do the same...as will a change in relative humidity. If the device isn't dead level and square to the gun, you can expect variations.
Enjoy your chronograph, but accept it for what it is. You can drive yourself to drink with one if you don't.
mgmorden
Member
I use a ProChrono Digital. Works well. The Shooting Chrony models do do that nifty fold-up thing though and they sell a nice case for them.
wally
Member
I used to chrono a lot, combining my shooting and techno geek interests. I used a home built microcomputer based timing system and Oehler Research screens. The screens are the tricky part and back in the 80's a pair of Oehler's screens cost more than his $80 Chrony F1 does today.
No load that grouped well ever showed a SD for a 10 shot string of more than 50 (most of what I measured with SD above 40 were factory loads with WW "silvertip" 140gr .357Mag being the worst at 50). My " standard" loads chrono's all had SDs under 20 looking back at my records.
I've standardized my loads and not changed in a long time, I find the chrono is more trouble than its worth these days because velocity is way less important than how the rounds actually group at the distance of interest.
At long range, no load with a large velocity variance will group well (vertical stringing) so the chrono doesn't really tell you anything unless you think a velocity measurement and a ballistics calculator will be more useful than actually shooting for groups at the intended distance.
No load that grouped well ever showed a SD for a 10 shot string of more than 50 (most of what I measured with SD above 40 were factory loads with WW "silvertip" 140gr .357Mag being the worst at 50). My " standard" loads chrono's all had SDs under 20 looking back at my records.
I've standardized my loads and not changed in a long time, I find the chrono is more trouble than its worth these days because velocity is way less important than how the rounds actually group at the distance of interest.
At long range, no load with a large velocity variance will group well (vertical stringing) so the chrono doesn't really tell you anything unless you think a velocity measurement and a ballistics calculator will be more useful than actually shooting for groups at the intended distance.
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ny32182
Member
Second 1911tuner in that you need to eliminate as many variables as possible to get consistent results, primarily with the lighting, and the angle at which you are shooting over it. It is measuring the horizontal component of velocity only, relative to the device. This means that if you are shooting at any upward or downward angle over it, you are losing velocity in the reading vs the actual/real muzzle velocity.
Also you need to use the sky screens unless it is a very overcast day, and also make sure, if in direct sunlight, you are not shooting at an angle to the sun that will allow the bullet to cast a shadow over the senors. I've read many times that this can trip the sensor in error, and it makes sense.
Using these methods, I feel like I've got pretty good results out of my Prochrono Digital. Environmental factors such as temp, etc, cause actual variations in the bullet velocity, so I'd be more concerned if I did not see the readings change as the ambient condidtions change.
This is one thing were I don't know that you are better served spending a bunch of money vs. buying a cheap one. The actual measurement technology is basically the same in all of them from what I can tell, and with the top end models you are paying for more automated features. Are you going to use these features? That is a question only you can answer. Personally I don't really have a need for them.
Also you need to use the sky screens unless it is a very overcast day, and also make sure, if in direct sunlight, you are not shooting at an angle to the sun that will allow the bullet to cast a shadow over the senors. I've read many times that this can trip the sensor in error, and it makes sense.
Using these methods, I feel like I've got pretty good results out of my Prochrono Digital. Environmental factors such as temp, etc, cause actual variations in the bullet velocity, so I'd be more concerned if I did not see the readings change as the ambient condidtions change.
This is one thing were I don't know that you are better served spending a bunch of money vs. buying a cheap one. The actual measurement technology is basically the same in all of them from what I can tell, and with the top end models you are paying for more automated features. Are you going to use these features? That is a question only you can answer. Personally I don't really have a need for them.
Agreed. It is good for making sure you are close to what you want, and you are right, you can shoot loads back to back, and it will be a little different. I take all the velocities with a grain of salt. Some days I just have to throw the data out.
I am real picky about getting it set up the same each time, but it is impossible to get it exactly the same each time.
Useful tools, but not the final word.
I have a Pro Chrono Digital, and it works well for me.
I do not recommend the RCBS Ammo Master. Bought one and have not used it yet.
However when I got into the manual the thing records data as ten shot strings. So, if I decide to shoot 7 rounds of one type of ammunition and five of a next, I have to figure out the start and stop point of the data strings at home.
Apparently it records ten strings of ten shots. If I want to shoot a 50 shot string of pistol ammunition, I will have to enter the data into a spread sheet at home to get a 50 shot velocity average.
http://www.midwayusa.com/product/911572/rcbs-ammomaster-chronograph
However when I got into the manual the thing records data as ten shot strings. So, if I decide to shoot 7 rounds of one type of ammunition and five of a next, I have to figure out the start and stop point of the data strings at home.
Apparently it records ten strings of ten shots. If I want to shoot a 50 shot string of pistol ammunition, I will have to enter the data into a spread sheet at home to get a 50 shot velocity average.
http://www.midwayusa.com/product/911572/rcbs-ammomaster-chronograph
All of the reasonably priced chronographs will get you what you want. Each has its own idiosyncrasies with seeing the bullet. Sometimes set-up is easy, sometimes not so easy. Mine gave me fits on Saturday as it was partly cloudy and the trees around my shooting position are fuller this year than normal.
I prefer a chronograph where the brains are not in harms way. It is not if you shoot out your chronograph but when.
With all the variables, data from different sessions will not be the same but should be close. Sometimes conditions (temperature, different components, etc) will give an indication of why the data is higher or lower than before.
I have had three different Chronys, two expired from lead poisoning. I still have the third. I currently use a CED M2. Data from the M2 can be directly downloaded to a computer, which I like.
The Chronys and the M2 gave me good data. The price you pay will depend on the what options you want.
I prefer a chronograph where the brains are not in harms way. It is not if you shoot out your chronograph but when.
With all the variables, data from different sessions will not be the same but should be close. Sometimes conditions (temperature, different components, etc) will give an indication of why the data is higher or lower than before.
I have had three different Chronys, two expired from lead poisoning. I still have the third. I currently use a CED M2. Data from the M2 can be directly downloaded to a computer, which I like.
The Chronys and the M2 gave me good data. The price you pay will depend on the what options you want.
armoredman
Member
I had a Chrony F-1. It selflessly jumped in front of a bullet to save the life of an innocent piece of paper. I hate suicidal equipment.
I have a ProChrono, seems to work just fine. I use it to see if my loads are "in the ballpark" compared to factory loads and velocities suggested by reloading data. It's sometimes interesting to find out what factory loads really do in my firearms.
I have a ProChrono, seems to work just fine. I use it to see if my loads are "in the ballpark" compared to factory loads and velocities suggested by reloading data. It's sometimes interesting to find out what factory loads really do in my firearms.
I like to "calibrate" all my firearms with factory ammunition if it is available for close to what I am loading.
Offfhand
Member.
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- Apr 12, 2009
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The Gold Standard of amateur class chronographs is the Oehler 35P. They stopped making them for a while and the prices for used ones on eBay went wild. So now they are in production again, costing more than most chronos but you get what you pay for. Their service is unbeatable.
MtnCreek
Member
I have told several people here that the CED has been a great chrony for me. Saturday morning, it clocked 9mm - 115gr FMJ's - 6.3gr Powerpistol at ~450fps, ~800 fps and Error. 
denton
Member
The sources of error in the chronograph itself are fairly simple:
1. Variation in the crystal clock frequency. That's something like 25 PPM per degree C, and is negligible.
2. Distance between the photocells. Most designs make this a negligible source of error.
3. Squareness of the photocell mounting. This is a fairly big issue. Because of this, it's hard to get the error in the effective spacing of the photocells down under plus or minus 1/8".
Beyond that, you have all the following errors to deal with:
1. Temperature of the barrel near the breech. If that isn't strictly controlled, it's a fairly major source of error.
2. Lighting conditions. If you're shooting on a sunny day and a cloud starts to obscure the sun, your readings will drop. The light is more diffuse, and this affects the squaring up of the electronic pulse generated as the bullet passes over the cells.
3. Extension rods. Putting those on will cause your readings to drop.
4. Microphonic components. If your muzzle is too close to the chronograph, some of the components act as poor quality microphones and mess up your measurement.
Personally, I do my chronographing on days when I can see the shadow of the tripod, and between mid-morning and mid-afternoon. Usually, I strap a thermocouple to my barrel and actively control barrel temperature, and I don't use the extension rods. My resulting chronograph speeds are very consistent, and, as nearly as I can tell, accurate.
I'm doing a little mod to my Shooting Chrony. I'm adding ultra bright LEDs just behind the photocells, and replacing the diffusers with retroreflective tape that will direct the LED light back down to the photocells. I think that will reduce the lighting condition dependence, and it will let me shoot indoors.
1. Variation in the crystal clock frequency. That's something like 25 PPM per degree C, and is negligible.
2. Distance between the photocells. Most designs make this a negligible source of error.
3. Squareness of the photocell mounting. This is a fairly big issue. Because of this, it's hard to get the error in the effective spacing of the photocells down under plus or minus 1/8".
Beyond that, you have all the following errors to deal with:
1. Temperature of the barrel near the breech. If that isn't strictly controlled, it's a fairly major source of error.
2. Lighting conditions. If you're shooting on a sunny day and a cloud starts to obscure the sun, your readings will drop. The light is more diffuse, and this affects the squaring up of the electronic pulse generated as the bullet passes over the cells.
3. Extension rods. Putting those on will cause your readings to drop.
4. Microphonic components. If your muzzle is too close to the chronograph, some of the components act as poor quality microphones and mess up your measurement.
Personally, I do my chronographing on days when I can see the shadow of the tripod, and between mid-morning and mid-afternoon. Usually, I strap a thermocouple to my barrel and actively control barrel temperature, and I don't use the extension rods. My resulting chronograph speeds are very consistent, and, as nearly as I can tell, accurate.
I'm doing a little mod to my Shooting Chrony. I'm adding ultra bright LEDs just behind the photocells, and replacing the diffusers with retroreflective tape that will direct the LED light back down to the photocells. I think that will reduce the lighting condition dependence, and it will let me shoot indoors.
Lost Sheep
Member
I don't know. I've never gone drinking with my chronograph. Lousy conversationalist and never buys a round.
The lining up in sequence (or even side-by-side, with the sensors overlapping their fields of view) is something I have wanted to try. How much difference? and was the difference consistent? Interesting experiment.
Another possible cause of variation is if the Chrony brand (which folds in the middle) is not completely opened up, the sensors will read a MUCH higher velocity the higher the bullet is over the sensors.
I would expect a temperature variation to make a difference in velocity. Chemical reactions do depend on temperature and generally, greater temperatures give higher velocities. With some powders, if you get cold enough, you get no velocity at all.
You bring up a lot of good points. Thanks.
Lost Sheep
Jdillon
Member
Used a Chrony for a number of years but was starting to get some inconsistent readings. Bought a an Oehler 35P about a year ago and very pleased with it. It is bulky and takes more time to set up but has been very consistent in its readings. I align it with a laser bore sighter so the bullet path travels over the three sensors at approximately the same point. I also measure the distance (10') from the bore to the first sensor.
Jim Watson
Member
I had a CED Millennium (version 1) which had a lot of bells and whistles, but I had to get the extra $ IR illuminator to be sure of getting a reading if the ambient light was not Just Right. It also had a lot of bits and pieces to assemble.
I now use a CE Pro Chrono Digital and find it easy to use. I am going to get the remote control the next time they are on sale.
I now use a CE Pro Chrono Digital and find it easy to use. I am going to get the remote control the next time they are on sale.
Lost Sheep
Member
When I first started shooting, chronographs used paper screens with wires embedded in them. They were expensive, you couldn't see your target downrange and had to keep replacing the screens as they got shot out. I never got one. Too expensive and too much trouble.
Now, we have skyscreens and costing less than $100 for functional accuracy. Or more bucks for more bells and whistles, printouts, statistical analysis and stuff.
The two latest things are the infra-red sensors (from C.E.D. as far as I know, the only one) and this one:
http://www.magnetospeed.com/products/magnetospeed-v1-ballistic-chronograph
Has anyone used one of these?
Me? I want one that uses a radar gun to clock the bullets. That way there is no sensor downrange to collect a stray bullet, muzzle blast should be less of a concern and lighting conditions would be totally irrelevant.
Hear me out there, inventors?
Lost Sheep
Now, we have skyscreens and costing less than $100 for functional accuracy. Or more bucks for more bells and whistles, printouts, statistical analysis and stuff.
The two latest things are the infra-red sensors (from C.E.D. as far as I know, the only one) and this one:
http://www.magnetospeed.com/products/magnetospeed-v1-ballistic-chronograph
Has anyone used one of these?
Me? I want one that uses a radar gun to clock the bullets. That way there is no sensor downrange to collect a stray bullet, muzzle blast should be less of a concern and lighting conditions would be totally irrelevant.
Hear me out there, inventors?
Lost Sheep
YankeeFlyr
Member
F1 Chrony
Love it!
Was skeptical at first but it's been great.
Love it!
Was skeptical at first but it's been great.
1911Tuner
Moderator Emeritus
On the angle of the bullet's path across the eyes or screens...there's one that you can't eliminate unless you fire the gun from a machine rest. Movement of the gun in recoil. That will always send the bullet through at an angle, and give a lower reading than the actual velocity. The other part is that in order to keep from measuring the shock wave, the gun has to be some distance from the device, which also gives a lower reading than actual velocity at the muzzle. To kinda/sorta compensate for these variables, I generally add 15 fps across the board.
jfdavis58
Member
Chronographing is a benign exercise that does more for imprinting a proper sight picture than is does for verifying the velocity of a bullet. I have four different chronographs and access to a fifth laboratory grade device; none ever register the same results unless huge sample sizes are involved, statistics are properly applied and a fair degree of subjective judgement is used to interpret the results---all three elements critical to the process.
Sample sizes of 5-10 rounds, especially with the typical statistical calculation follow-on are little more than silly musings. Learn statistics; such exercises make for interesting learning tools but have little real meaning. Sample sizes between forty and fifty rounds would be needed to ascertain a statistically meaningful difference when one has a set of basis numbers; comparing two random samples probably introduces more user variation than can be offset by even the best statistics or testing 'techniques'.
The angle of bullet departure, one round relative to the next generates no meaningful results even with statistics-do the math. In simple terms the difference caused by different path lengths over the screens is smaller than the intrinsic noise of the electronics involved in measuring and computing a human form result---i.e within the accuracy of the typical devices. Do the math.
The reasons for not chronographing by shooting up or down a hill have more to do with the apparent shortening or lengthening of the bullets ballistic trajectory; a simple parabola with associated and comprehensible mathematical description most quickly forgot or never learned. Regardless, common sense says you don't compound one difficult problem upon another (with out good reason); why chronograph shooting up or down a hill?
All sun based detection devices dislike direct sunlight. Hence the diffusers some makers include. The process of detecting the passage depends on a smeared shadow-it's an integration problem (with statistics). A sharp edged shadow doesn't provide as dependable an integration result as a smeared shadow. Fifty to seventy five percent cloud cover, no wind days with temperature and humidity at either similar levels to your loading conditions or levels like your intended shooting conditions (with judicious allowances for 'not quite exactly') the same conditions yielding the best results in shooting sports like IPSC/USPSC and in hunting.
Any strong light (interacting with the sensors) with a power source of alternating current will skew or ruin results--especially true with IR based sensors but also more readily apparent in the outputted numbers. Also true with any RF emanating generator or alternator but that doesn't affect the sensor as much as it does the electronics.
It's in the manual. If you read manuals like many, like many who use the throne room for their most serious reading, you will finish your nature call, wipe, zip and flush long before you reach the notes in the back of the manual where tips and hints are most often located. You will know how to use the device but not well.
There are also similarly located warnings about the need for fresh batteries.
Distance from muzzle to first screen can compensate (at the expense of knowing true muzzle velocity) for the muzzle blast and sonic shock wave that destroy accurate measurement. A piece of round AC duct-work and a sheet of peg board can do the same while additionally allowing you to visualize the 'tunnel' through which the bullet must pass for good readings. Note: it is especially important that the true point of impact align well with the standard point of aim; when using a scoped rifle this along with accurate height of sightline over center of bore becomes critically important.
A ballistics program can be used in a trial and error fashion to back 'calculate' a true muzzle velocity. With a rifle it's more fun to buy an extra box of shells and some extra targets and do the follow-on trajectory calculation process empirically; added-- it's really about the real practice benefit. It doesn't matter with typical defensive style handguns.
From all this you may conclude chronographing to be wasted time.
Not at all.
It is good for determining trends or more accurately, that your loading is following the correct trend. I.e more powder means more velocity all else being equal. And that your recordkeeping and ammo labeling are concise and accurate.
It can also be used to know 'this powder won't work' when a specific velocity (say for a power factor) is required.
It can detect (with the proper math and interpretation) when some particular re-manufacturing improvement (say trimming, neck turning, primer pocket reaming and truing etc) is affecting velocity average. The same sample size considerations apply to any follow-on statistical calculation as allude previously.
Considering the cost of a unit, it always improves your sighting, triggering and other shot delivery performances.
It's fun to see how much difference can be expected when shooting the same ammo under two different conditions (as long as a trophy is NOT at stake) or from two different firearms.
YMMV, something clearly demonstrated by other contributors.
Sample sizes of 5-10 rounds, especially with the typical statistical calculation follow-on are little more than silly musings. Learn statistics; such exercises make for interesting learning tools but have little real meaning. Sample sizes between forty and fifty rounds would be needed to ascertain a statistically meaningful difference when one has a set of basis numbers; comparing two random samples probably introduces more user variation than can be offset by even the best statistics or testing 'techniques'.
The angle of bullet departure, one round relative to the next generates no meaningful results even with statistics-do the math. In simple terms the difference caused by different path lengths over the screens is smaller than the intrinsic noise of the electronics involved in measuring and computing a human form result---i.e within the accuracy of the typical devices. Do the math.
The reasons for not chronographing by shooting up or down a hill have more to do with the apparent shortening or lengthening of the bullets ballistic trajectory; a simple parabola with associated and comprehensible mathematical description most quickly forgot or never learned. Regardless, common sense says you don't compound one difficult problem upon another (with out good reason); why chronograph shooting up or down a hill?
All sun based detection devices dislike direct sunlight. Hence the diffusers some makers include. The process of detecting the passage depends on a smeared shadow-it's an integration problem (with statistics). A sharp edged shadow doesn't provide as dependable an integration result as a smeared shadow. Fifty to seventy five percent cloud cover, no wind days with temperature and humidity at either similar levels to your loading conditions or levels like your intended shooting conditions (with judicious allowances for 'not quite exactly') the same conditions yielding the best results in shooting sports like IPSC/USPSC and in hunting.
Any strong light (interacting with the sensors) with a power source of alternating current will skew or ruin results--especially true with IR based sensors but also more readily apparent in the outputted numbers. Also true with any RF emanating generator or alternator but that doesn't affect the sensor as much as it does the electronics.
It's in the manual. If you read manuals like many, like many who use the throne room for their most serious reading, you will finish your nature call, wipe, zip and flush long before you reach the notes in the back of the manual where tips and hints are most often located. You will know how to use the device but not well.
There are also similarly located warnings about the need for fresh batteries.
Distance from muzzle to first screen can compensate (at the expense of knowing true muzzle velocity) for the muzzle blast and sonic shock wave that destroy accurate measurement. A piece of round AC duct-work and a sheet of peg board can do the same while additionally allowing you to visualize the 'tunnel' through which the bullet must pass for good readings. Note: it is especially important that the true point of impact align well with the standard point of aim; when using a scoped rifle this along with accurate height of sightline over center of bore becomes critically important.
A ballistics program can be used in a trial and error fashion to back 'calculate' a true muzzle velocity. With a rifle it's more fun to buy an extra box of shells and some extra targets and do the follow-on trajectory calculation process empirically; added-- it's really about the real practice benefit. It doesn't matter with typical defensive style handguns.
From all this you may conclude chronographing to be wasted time.
Not at all.
It is good for determining trends or more accurately, that your loading is following the correct trend. I.e more powder means more velocity all else being equal. And that your recordkeeping and ammo labeling are concise and accurate.
It can also be used to know 'this powder won't work' when a specific velocity (say for a power factor) is required.
It can detect (with the proper math and interpretation) when some particular re-manufacturing improvement (say trimming, neck turning, primer pocket reaming and truing etc) is affecting velocity average. The same sample size considerations apply to any follow-on statistical calculation as allude previously.
Considering the cost of a unit, it always improves your sighting, triggering and other shot delivery performances.
It's fun to see how much difference can be expected when shooting the same ammo under two different conditions (as long as a trophy is NOT at stake) or from two different firearms.
YMMV, something clearly demonstrated by other contributors.
I use small samples, and understand the limitations. I can gain enough info with them to know if I am close to something. No use wasting too many rounds until I think I have something. I have tested some loads using small samples on different days and the numbers have been close enough to be statistically indifferent. That is always a good sign. Some loads, not so much.
loneviking
Member
I recently bought a ProChrono digital as my first chrono. Bought a small tripod with a level on it, put the chrono on the tripod and its ready to go. I'm happy with it and wish I had bought one a couple of years ago when I first started reloading. I now have a good idea when a load is in the ballpark for acceptable speed with a particular charge of powder.
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