standard deviation and accuracy
- Thread starter dogone
- Start date
When I did a ladder test for my .260 I found a certain range of loads fell very tightly into the same horizontal plane. Out of that range of 'tight' loads I picked the mid point. One batch of reloads were hastily put together and the SD was rather high, yet this didn't really show up at long range as much as one would have thought. Could it be that if your loads fall in the sweet spot for your barrel, the mid point of the most consistent loads in your ladder test, that any SD either side of the mid point is 'absorbed', sort of having some wiggle room for inconsistency. That's my theory for why SD doesn't always effect accuracy as much as we would think.
Don't get me wrong, the theory of SD making a difference is sound, but sometimes theory is in conflict with reality, and I'll take reality hands down every time, after all isn't that the point of 'truing' ballistic data?
Don't get me wrong, the theory of SD making a difference is sound, but sometimes theory is in conflict with reality, and I'll take reality hands down every time, after all isn't that the point of 'truing' ballistic data?
I'm using the CED M2 these days, to say that I am getting more consistant data is an understatement. All of my "true ballistic data" is making sense now. You are better not using a chronograph at all than trying to make sense of one that is giving inconsistant readings.
While I have never tested my chronograph both indoors and out with the exact same load as you suggested I dont see the point in such a test. The value that I see in a chronograph for reloading purposes is to determine shot to shot variation under one lighting condition.
arcticcathonda
CGN frequent flyer
- Location
- Southern Alberta
So arguably when you chrony outside your shot to shot variation is now composed of variations in your loads as well as variations attributed to changes in ambient the light conditions. As static as we think the bright sunny blue bird days are, this is a myth.
Anyways, you have found a method that works for you and others have their own system! Hurray to shooting freedoms!
Actually I chronograph indoors under the same lighting conditions every time. I do use the lights that came with the chronogragh and turn off all the lights in the range that are near it. For my purposes the light is always exactly the same. Maybe that's why I never had a problem.
sask farmboy... maybe Jerry needs to come shoot with me. I have my share of medals on the wall. I fear nobody.
I find it real interesting that so many of you are jumping on the basic notion that chronographs are junk without a single one of you presenting some reasonable shread of proof.
I read it somewhere is not good enough.
My grandfather told me is not good enough.
Some guy who shot at a mile with a 17 fireball told me is not good enough.
I read it 200 times on CGN is not good enough.
One of you please, share it with us all how you KNOW the chronograph is not accurate.
How about putting 3 chronographs in front of each other and shooting the same bullet through all of them?
Anybody ever try that?
C'mon... Whatcha got?
I find it real interesting that so many of you are jumping on the basic notion that chronographs are junk without a single one of you presenting some reasonable shread of proof.
I read it somewhere is not good enough.
My grandfather told me is not good enough.
Some guy who shot at a mile with a 17 fireball told me is not good enough.
I read it 200 times on CGN is not good enough.
One of you please, share it with us all how you KNOW the chronograph is not accurate.
How about putting 3 chronographs in front of each other and shooting the same bullet through all of them?
Anybody ever try that?
C'mon... Whatcha got?
Mystic Precision
CGN Ultra frequent flyer
- Location
- Summerland, BC
Take a Chronie brand. set it up with the provided shades on any given day.
Make up a batch of ammo, shoot a few rds in the morning, afternoon and evening. compare the numbers. did they vary from set to set?
Try on a cloudy day, sunny day. Do the numbers agree with past numbers?
Has the Chronie manf changed their specs on their clocks. Last time I saw a spec it was 0.5% of output.
YMMV
Jerry
Make up a batch of ammo, shoot a few rds in the morning, afternoon and evening. compare the numbers. did they vary from set to set?
Try on a cloudy day, sunny day. Do the numbers agree with past numbers?
Has the Chronie manf changed their specs on their clocks. Last time I saw a spec it was 0.5% of output.
YMMV
Jerry
There's a loose group of us that shoot together and compare notes a lot. The 3 chronies we had were lucky to read within 100 fps of each other. One read 100 slower and another read 100 faster than mine. Junk.
I watched another aquaintance (he's not the type who has friends) clock speeds about 300 fps faster than had previously been shot out of the same lot of custom loaded 300 WSM. I saw his notes. An hour later the speeds dropped back to the previous believeable velocity. Same box of shells, 300 fps difference in an hour.
Another occasion, same range. Ever see a .300 win push 180s at 3500 fps with 75 grains of RL22? It didn't do it before the sun got low, never did it again. Mine does 3150 if you care.Or if you believe a chrony. Or if you pick the medium speed one.Or if you pick the shots you like out of the garbage ones, and those that work at all. You can trust the SD and ES numbers from a chrony if you want; personally I wouldn't bet a dollar on one working three time in a row.
My chrony is in a landfill. Good place for it.
I watched another aquaintance (he's not the type who has friends) clock speeds about 300 fps faster than had previously been shot out of the same lot of custom loaded 300 WSM. I saw his notes. An hour later the speeds dropped back to the previous believeable velocity. Same box of shells, 300 fps difference in an hour.
Another occasion, same range. Ever see a .300 win push 180s at 3500 fps with 75 grains of RL22? It didn't do it before the sun got low, never did it again. Mine does 3150 if you care.Or if you believe a chrony. Or if you pick the medium speed one.Or if you pick the shots you like out of the garbage ones, and those that work at all. You can trust the SD and ES numbers from a chrony if you want; personally I wouldn't bet a dollar on one working three time in a row.
My chrony is in a landfill. Good place for it.
I was not commenting on all chronographs, I was commenting on the "Chrony" brand specifically. I'm sure there are quite a few good chronographs out there, I believe the CED M2 that I use now to be quite accurate, maybe it isn't exact but when I compare the velocities and computer generated drop data with my actual tested performance it works. My "Chrony" brand could not achieve these same results. The velocities of the "Chrony" would not work with the actual tested drop data.
I have heard good things about the "Ohler" brand as well but I have never used one so I can't comment on them.
While these results were not scientifically tested, they work in my calculations and the system I have been using.
Mystic Precision
CGN Ultra frequent flyer
- Location
- Summerland, BC
Oehler is still the gold standard IF you can find one and not afraid of the price tag.
Next up is the CED. This is an affordable unit that is getting solid reviews from those that know a thing or two about external ballistics. If a shooters want to work on the numbers and stats of shooting, give me a PM or email as I can supply
Then a big step to the generic CHRONOGRAPH. Some good, some not, some work, some dont. One thing in common, they all vary based on the light presented.
And they all use clocks with a built in error larger then the values we are trying to crunch.
Do I still have my CHRONIE? Yes. I use it just to make sure I am not being a hero and load to sane performance levels. The numbers generated will be in the right ballpark - output of 2800fps doesn't mean 2000 or 3500fps. The actual number may be 2768 or 2847. Doesn't matter cause it is a workable number to let my drop chart put in on paper.
Jerry
Next up is the CED. This is an affordable unit that is getting solid reviews from those that know a thing or two about external ballistics. If a shooters want to work on the numbers and stats of shooting, give me a PM or email as I can supply
Then a big step to the generic CHRONOGRAPH. Some good, some not, some work, some dont. One thing in common, they all vary based on the light presented.
And they all use clocks with a built in error larger then the values we are trying to crunch.
Do I still have my CHRONIE? Yes. I use it just to make sure I am not being a hero and load to sane performance levels. The numbers generated will be in the right ballpark - output of 2800fps doesn't mean 2000 or 3500fps. The actual number may be 2768 or 2847. Doesn't matter cause it is a workable number to let my drop chart put in on paper.
Jerry
I sent an email to Chrony asking about the performance they say I can expect and this is thier response...
"The 99.5 percent accuracy is compared to much more expensive laboratory-grade chronographs with wider spaced photosensors and controlled lighting conditions set up and used by experienced technicians. That means if a Shooting Chrony and a laboratory-grade chronograph measure the same bullet velocity of about 3000fps, they would both agree within 15 fps (i.e.
plus or minus 15 fps). So if the laboratory-grade chronograph reported exactly 3000 fps, a Shooting Chrony measuring the same bullet might report
3000 fps or it might report as high as 3015 fps or as low as 2985 fps. See the math below:
3000 X 0.995 = 2985
3000 - 2985 = 15
"
So basically they claim you can expect plus or minus 15 fps from Chrony.
The web site for PVM-21 claims only 1 percent accuracy - actually less accurate than Chrony claims. Could be they are just being conservative or something else.
On their web site oehler-research claims accuracy as per this table per distance between the sensors..
3000 FPS @ 1ft apart 16 fps, @ 2ft apart 8 fps, @ 4ft apart 4 fps, @ 8ft apart 2 fps so if the sensors are only 1 ft apart they claim to be no more accurate than a chrony. The benefit of the oehler-research moel is that you can spread out the sensors to improve the accuracy of the results and at 8 ft apart is pretty much dead on.
"The 99.5 percent accuracy is compared to much more expensive laboratory-grade chronographs with wider spaced photosensors and controlled lighting conditions set up and used by experienced technicians. That means if a Shooting Chrony and a laboratory-grade chronograph measure the same bullet velocity of about 3000fps, they would both agree within 15 fps (i.e.
plus or minus 15 fps). So if the laboratory-grade chronograph reported exactly 3000 fps, a Shooting Chrony measuring the same bullet might report
3000 fps or it might report as high as 3015 fps or as low as 2985 fps. See the math below:
3000 X 0.995 = 2985
3000 - 2985 = 15
"
So basically they claim you can expect plus or minus 15 fps from Chrony.
The web site for PVM-21 claims only 1 percent accuracy - actually less accurate than Chrony claims. Could be they are just being conservative or something else.
On their web site oehler-research claims accuracy as per this table per distance between the sensors..
3000 FPS @ 1ft apart 16 fps, @ 2ft apart 8 fps, @ 4ft apart 4 fps, @ 8ft apart 2 fps so if the sensors are only 1 ft apart they claim to be no more accurate than a chrony. The benefit of the oehler-research moel is that you can spread out the sensors to improve the accuracy of the results and at 8 ft apart is pretty much dead on.
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Just making an observation regarding some of the comments about testing the same load over the chronograph at different times of the day and finding variations in chronograph reported speeds... There is no way of knowing if the chronograph is the cause of the change in reported speed or if there is an actual speed change. The speed can change due to temperature of the air, barometric pressure, temperature of the barrel, buildup of copper, buildup of carbon, temperature of the ammunition, weight of the brass, inconstancies in primers etc.
As for using drop at a distance I have consistently found different vertical settings required at the same distance on the same day at different times of the day with the exact same ammo. So why is that happening? Is it atmospheric meaning sun, wind or barometric pressure or is my muzzle velocity changing due to temperature or some other thing? We simply have no way to be certain.
I did come across a thread on snipers hide where a guy shot each bullet through 2 chronographs that were directly in front of each other and reported the results from each chronograph and there were disagreements but for the most part were relatively minor. I would not say the results would be justification for using the chrony as a paper weight and I would not say the "better" of the two was definitively better in that particular test. The test also did not describe how the chronographs were set up, in the dark with lights or just outside in direct sunlight.
I know that some of the more expensive chronographs out there are actually 2 chronographs joined as a single unit and it compares the speed determined between the 2 reported speeds and averages them out. The result is thought to be more correct. The same unit reports when there is a wide disagreement between the 2 speed sensing units - so you as a user might choose to disregard that particular value.
I would think that a guy can do the same thing by using 2 chrony's for less invested and get very similar results. Just record the values in an MS Excel spreadsheet and do the math.
Another option for the more creative is to separate the chrony at the hinge and double the distance between the sensors. Then just double the reported speed to determine the actual speed. It would then by default be twice as accurate.
I found a video on You Tube comparing the two called
“Chronograph Shootout: Chrony F-1 Master vs Oehler 35P”
One thing I don’t like about this test is he did not reverse the location of the chrony from front to back at the half way point. That leaves muzzle blast as a potential contaminator with the chrony in the disadvantaged position for the entire test. This test is also in daylight which is not ideal.
As for using drop at a distance I have consistently found different vertical settings required at the same distance on the same day at different times of the day with the exact same ammo. So why is that happening? Is it atmospheric meaning sun, wind or barometric pressure or is my muzzle velocity changing due to temperature or some other thing? We simply have no way to be certain.
I did come across a thread on snipers hide where a guy shot each bullet through 2 chronographs that were directly in front of each other and reported the results from each chronograph and there were disagreements but for the most part were relatively minor. I would not say the results would be justification for using the chrony as a paper weight and I would not say the "better" of the two was definitively better in that particular test. The test also did not describe how the chronographs were set up, in the dark with lights or just outside in direct sunlight.
I know that some of the more expensive chronographs out there are actually 2 chronographs joined as a single unit and it compares the speed determined between the 2 reported speeds and averages them out. The result is thought to be more correct. The same unit reports when there is a wide disagreement between the 2 speed sensing units - so you as a user might choose to disregard that particular value.
I would think that a guy can do the same thing by using 2 chrony's for less invested and get very similar results. Just record the values in an MS Excel spreadsheet and do the math.
Another option for the more creative is to separate the chrony at the hinge and double the distance between the sensors. Then just double the reported speed to determine the actual speed. It would then by default be twice as accurate.
I found a video on You Tube comparing the two called
“Chronograph Shootout: Chrony F-1 Master vs Oehler 35P”
One thing I don’t like about this test is he did not reverse the location of the chrony from front to back at the half way point. That leaves muzzle blast as a potential contaminator with the chrony in the disadvantaged position for the entire test. This test is also in daylight which is not ideal.
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back40sniper
CGN Regular
- Location
- South east Sask.
Oehler is still available, just order direct.
I have had the same experience I have a 300 rum and anywhere from 88.5g to 90.5 of retumbo seems to drop the bullets in a tight group (even though the speeds are slightly off) anything less or anything more produces some varying results approximately .25" difference at 100y per grains although for some reason with this powder I cant seem to get lower than a 30sd, now I know what your all gonna say, somethings off, neck tension or something. but using the same fired brass, seating depth and bullets using h50bmg powder I can get in the single digits sometimes and max 20fps difference
