How do you interpret your Chronograph Data?

E

esmith

New member
Just curious, I borrowed a friend's F-1 Chrony today, and tested some rounds I'm going to take hunting. I'll freely admit, this step in the process is new to me, I've gotten along fine, but couldn't pass this offer up. Owning a Chrono hasn't yet occured, although it will some day.

Wondered if you wise ones have any rules of thumb on how you interpret your chrono data.

I am loading with Hodgdon Benchmark Powder through a Dillon 550 with auto powder measure. Taking no particular steps to increase consistency, other than simply loading carefully and smoothly on the press. The measure as most Dillon owners know, is accurate to about 0.100 of a grain of powder.

My standard deviation in the 10 shot string is 23.77 fps.

If I throw out the high and low rounds my SD is 15.95 fps. The average then only changes by 0.075, so I take that as a good sign.

Is that good, bad considering? What do you hope/aim for assuming a similar loading process?
 
It really depends a bit on the range you are shooting. I think you will find if you shot a factory laod across the screens the deviations would be very close and they kill a lot of game with factory loads. Anything under 30 SD in most hunting applications would be GTG in my book. Now for extremelong range target stuff that would never do. The ES and SD would need to be as low as possible then delving below 10-12. .

Also the bore condition is important on results. Was it a squeaky clean bore to start? Was the first shot out of the barrel one of the two problem children?

Greg
 
Originally Posted By: esmithJust curious, I borrowed a friend's F-1 Chrony today, and tested some rounds I'm going to take hunting. I'll freely admit, this step in the process is new to me, I've gotten along fine, but couldn't pass this offer up. Owning a Chrono hasn't yet occured, although it will some day.

Wondered if you wise ones have any rules of thumb on how you interpret your chrono data.

I am loading with Hodgdon Benchmark Powder through a Dillon 550 with auto powder measure. Taking no particular steps to increase consistency, other than simply loading carefully and smoothly on the press. The measure as most Dillon owners know, is accurate to about 0.100 of a grain of powder.

My standard deviation in the 10 shot string is 23.77 fps.

If I throw out the high and low rounds my SD is 15.95 fps. The average then only changes by 0.075, so I take that as a good sign.

Is that good, bad considering? What do you hope/aim for assuming a similar loading process?

The Dillon throws close to 1/10th of a grain - not 0.100 (which would be 1/1000th of a grain)

Chronographs are not as accurate or as repeatable as people think, so don't get all wrapped up in SD and other numbers... also, you can't delete two numbers to make it look good - there are no fliers in 5 shot groups, or in chronograph's SD figures. It all counts.

Use them for average velocities and go with it.
 
.1=1/10, .01=1/100, .001=1/1000. Cat I think you have the right number of zeros just in the wrong place.

I agree you can't throw numbers out to make your SD look good unless they are so far off as to be an error.

I just use the crono to check velocity to see if the load is in the ballpark for the data I've used to develop the load. Accuracy isn't on the crono it is on the paper but it might help you find a reason for poor accuracy.
 
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Originally Posted By: AWS.1=1/10, .01=1/100, .001=1/1000. Cat I think you have the right number of zeros just in the wrong place.

No... engineering notation is that the accuracy of the measurement is determined by he numbers of digits and zeros behind the decimal place

0.1 is 1/10th, accurate to +/- 0.04

0.100000000000 is one 1/10th, accurate to 4 ten/trillionths
 
Originally Posted By: GLShooterIt really depends a bit on the range you are shooting. I think you will find if you shot a factory laod across the screens the deviations would be very close and they kill a lot of game with factory loads. Anything under 30 SD in most hunting applications would be GTG in my book. Now for extremelong range target stuff that would never do. The ES and SD would need to be as low as possible then delving below 10-12. .

Also the bore condition is important on results. Was it a squeaky clean bore to start? Was the first shot out of the barrel one of the two problem children?

Greg



I see. I did fire some xm193 to practice getting readings. It was very consistent more so than my loads... for five shots anyway. I was happy with my results having no idea prior how I was doing.

The bore was fouled when I began my ten shot string. It had shot 25 rounds earlier in the day. I like to mimic actual hunting conditions. In this case most of my pdog shots will be from a dirty barrel.

My hit % last trip was good enough for me. Now it will be more fun knowing my speeds somewhat (not including temp and other variables)
 
Originally Posted By: AWS "not 0.100 (which would be 1/1000th of a grain)"

Your post.


"not 0.100 (which would be 1/1000th of a grain"... accuracy!

The discussion/comment was how accurate the Dillon measure could throw..

The OP said, " is accurate to about 0.100 of a grain of powder."

It is not - it is accurate to 0.1 = 1/10th +/- 0.04gr
 
Cat is right. In Engineering, every number added behind a decimal denotes measurement.

0.1005 is much different than 0.10005

And 0.1 is one tenth.

Numbers have meaning. Just like words.

 
Originally Posted By: esmithOriginally Posted By: GLShooterIt really depends a bit on the range you are shooting. I think you will find if you shot a factory laod across the screens the deviations would be very close and they kill a lot of game with factory loads. Anything under 30 SD in most hunting applications would be GTG in my book. Now for extremelong range target stuff that would never do. The ES and SD would need to be as low as possible then delving below 10-12. .

Also the bore condition is important on results. Was it a squeaky clean bore to start? Was the first shot out of the barrel one of the two problem children?

Greg



I see. I did fire some xm193 to practice getting readings. It was very consistent more so than my loads... for five shots anyway. I was happy with my results having no idea prior how I was doing.

The bore was fouled when I began my ten shot string. It had shot 25 rounds earlier in the day. I like to mimic actual hunting conditions. In this case most of my pdog shots will be from a dirty barrel.

My hit % last trip was good enough for me. Now it will be more fun knowing my speeds somewhat (not including temp and other variables)

Speed kills and with those numbers and a few more you can flat put the speed on them.

Greg
 
Originally Posted By: GLShooterOriginally Posted By: esmithOriginally Posted By: GLShooterIt really depends a bit on the range you are shooting. I think you will find if you shot a factory laod across the screens the deviations would be very close and they kill a lot of game with factory loads. Anything under 30 SD in most hunting applications would be GTG in my book. Now for extremelong range target stuff that would never do. The ES and SD would need to be as low as possible then delving below 10-12. .

Also the bore condition is important on results. Was it a squeaky clean bore to start? Was the first shot out of the barrel one of the two problem children?

Greg



I see. I did fire some xm193 to practice getting readings. It was very consistent more so than my loads... for five shots anyway. I was happy with my results having no idea prior how I was doing.

The bore was fouled when I began my ten shot string. It had shot 25 rounds earlier in the day. I like to mimic actual hunting conditions. In this case most of my pdog shots will be from a dirty barrel.

My hit % last trip was good enough for me. Now it will be more fun knowing my speeds somewhat (not including temp and other variables)

Speed kills and with those numbers and a few more you can flat put the speed on them.

Greg

I probably don't know what I'm missing if I am, but a cheat sheet from Hornady's Ballistic Calculator website, with all the variables I can put in, and I should be a lot closer than just guessing. Muzzle velocity sounds great at 3661, but at 300 and 400 yards it isn't quite as impressive. Thats where most of our pdogs get hit at.

But these little 40 gr Noslers BT's should still have pretty good effect around the 2300 fps zone at that distance.
 
As for you meticulous types...

I meant 1/10th of a grain of gunpowder, as a beam scale would indicate.

I am not, nor do I find the personal need to be any more accurate. Mainly because I don't shoot that well
thumbup.gif
 
Originally Posted By: esmithAs for you meticulous types...

I meant 1/10th of a grain of gunpowder, as a beam scale would indicate.

I am not, nor do I find the personal need to be any more accurate. Mainly because I don't shoot that well
thumbup.gif



Point taken....

And you probably never will.
wink.gif
 
Originally Posted By: esmithOriginally Posted By: GLShooterOriginally Posted By: esmithOriginally Posted By: GLShooterIt really depends a bit on the range you are shooting. I think you will find if you shot a factory laod across the screens the deviations would be very close and they kill a lot of game with factory loads. Anything under 30 SD in most hunting applications would be GTG in my book. Now for extremelong range target stuff that would never do. The ES and SD would need to be as low as possible then delving below 10-12. .

Also the bore condition is important on results. Was it a squeaky clean bore to start? Was the first shot out of the barrel one of the two problem children?

Greg



I see. I did fire some xm193 to practice getting readings. It was very consistent more so than my loads... for five shots anyway. I was happy with my results having no idea prior how I was doing.

The bore was fouled when I began my ten shot string. It had shot 25 rounds earlier in the day. I like to mimic actual hunting conditions. In this case most of my pdog shots will be from a dirty barrel.

My hit % last trip was good enough for me. Now it will be more fun knowing my speeds somewhat (not including temp and other variables)

Speed kills and with those numbers and a few more you can flat put the speed on them.

Greg

I probably don't know what I'm missing if I am, but a cheat sheet from Hornady's Ballistic Calculator website, with all the variables I can put in, and I should be a lot closer than just guessing. Muzzle velocity sounds great at 3661, but at 300 and 400 yards it isn't quite as impressive. Thats where most of our pdogs get hit at.

But these little 40 gr Noslers BT's should still have pretty good effect around the 2300 fps zone at that distance.

With that table you will not be well liked at 400 and less by the PD's.

Greg
 
Originally Posted By: SmokelessOriginally Posted By: esmithAs for you meticulous types...

I meant 1/10th of a grain of gunpowder, as a beam scale would indicate.

I am not, nor do I find the personal need to be any more accurate. Mainly because I don't shoot that well
thumbup.gif



Point taken....

And you probably never will.
wink.gif


Not unless the 21 month old or the 6 week old becomes avid rifleman. Meanwhile, its pretty tough tearing attention away from them to go shooting. So my shooting isn't getting much better. But I force myself once in a while.
thumbup1.gif
 
Originally Posted By: GLShooter

With that table you will not be well liked at 400 and less by the PD's.

Greg

If I can ruin a pdog's day, then my job is done. Shooting starts Friday in North Dakota. Starting to lose sleep already. Been two years since I've been on a trip for them.
 
Originally Posted By: esmithOriginally Posted By: GLShooter

With that table you will not be well liked at 400 and less by the PD's.

Greg

If I can ruin a pdog's day, then my job is done. Shooting starts Friday in North Dakota. Starting to lose sleep already. Been two years since I've been on a trip for them.

Have fun and watch for snakes.

Greg
 
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