ES induced elevation @ 1K

[canderson]

I need a little help please. My f class fireforming loads are running about 2900 with an ES of 25. Chambering is a 6 Dasher shooting 108 Bergers. Approximately how much elevation difference will that equate to at 1000 yds. I shot some pretty good groups yesterday with the vertical spread greater than the horizontal. Trying to determine if that is me or my loads. Thanks in advance for any help.

Chris

 

[AJ Peacock]

It's pretty easy. Go to http://www.jbmballistics.com/~jbm/cgi-bin/jbmtraj_simp-5.0.cgi and enter your info and the low velocity. Set your site in at 100yds, then see what your drop is at 1000yds. Then repeat with the higher velocity. See what the difference in drop is. This is not exact, but pretty darn close.

For 2900fps (-310.8" drop) and 2875fps (-316.8" drop) for the .243 Berger 108gr Match BT, the vertical difference is 6.5" at 1000yds.

Hope this helps,
AJ

 

[canderson]

Thanks AJ,

I thought that is what I needed to do. I just wanted to verify my figures. I think my rest is giving me a little vertical at 1000. Thanks again.

Chris

 

[J E Custom]

It's pretty easy. Go to JBM - Calculations - Trajectory (Simplified) and enter your info and the low velocity. Set your site in at 100yds, then see what your drop is at 1000yds. Then repeat with the higher velocity. See what the difference in drop is. This is not exact, but pretty darn close.

For 2900fps (-310.8" drop) and 2875fps (-316.8" drop) for the .243 Berger 108gr Match BT, the vertical difference is 6.5" at 1000yds.

Hope this helps,
AJ

+1
Just remember to add the 6.5" to the MOA group size .

In other words if your rifle is capable of 1 MOA @ 1000yards, 10 inches+ 6.5inches= 16.5 inches
at 1000 yards would be your vertical dispersion.

SDs also effect windage a little and what you need is a SD of less than 10 if you can get it.

J E CUSTOM

 

[milanuk]

Just remember to add the 6.5" to the MOA group size .

In other words if your rifle is capable of 1 MOA @ 1000yards, 10 inches+ 6.5inches= 16.5 inches
at 1000 yards would be your vertical dispersion.

Ya know, I love discussions like this. By that sort of math, my gun would barely be able to hit the target, much less put 'em in the X-ring on anything resembling a consistent basis. gun)

Actually... errors don't stack linearly like that. In theory, they maybe *could*, but your chances are probably better of hitting the lottery. Root Sum of Squares (RSS) is a better method for figuring out how errors add up:

TotalError = sqrt((Error1)^2 + (Error2)^2 + (ErrorN)^2...)

or in this case...

sqrt((10)^2 + (6.5)^2) = ~11.9

Then add in that E.S. is a lousy measure of consistency, mathematically speaking. It's easy to calculate and simple for the average person to understand, but it gives too much (all) weight to two 'outlier' data points - the ones statistically least likely to occur on a regular, repeatable basis - so the actual effect on target is (in my experience) rarely as drastic as predicted by simply plugging the high and low ES numbers into a ballistics program.

There's something to be said for considering absolute worst-case scenarios where you would experience the actual total ES spread between two sequential shots, stacked squarely against the absolute worst possible spread between shots in the group... if you like worrying yourself into a lather and an upset stomach

YMMV,

Monte

 

[canderson]

Thanks for all of the replys. I have shot several 4 or 5 ten shot groups at 1000. They will probably average 4-5 inches left to right and 6.5-10 inches up and down. I was trying to determine if most of the vertical was in load tuning (because of ES of 25) or the operator. From what I have seen in shooting f class, you want a group that is wider than tall. I am open to any opinions on things to check out.
Thanks,
Chris

 

[AJ Peacock]

Thanks for all of the replys. I have shot several 4 or 5 ten shot groups at 1000. They will probably average 4-5 inches left to right and 6.5-10 inches up and down. I was trying to determine if most of the vertical was in load tuning (because of ES of 25) or the operator. From what I have seen in shooting f class, you want a group that is wider than tall. I am open to any opinions on things to check out.
Thanks,
Chris

I would guess that half your vertical is due to velocity spread.

AJ

 

[milanuk]

Maybe... I've had the unpleasant fortune of shooting at some ranges where *everybody* gets vertical shots. Sometimes just one 'spoiler' here or there, sometimes a whole slew of them. Those days will about make ya cry...

Anywho... it might be worth seeing if anyone else shooting the same range facility has had unexplained vertical problems - might not be just you...

 

[J E Custom]

Ya know, I love discussions like this. By that sort of math, my gun would barely be able to hit the target, much less put 'em in the X-ring on anything resembling a consistent basis. gun)

Actually... errors don't stack linearly like that. In theory, they maybe *could*, but your chances are probably better of hitting the lottery. Root Sum of Squares (RSS) is a better method for figuring out how errors add up:

TotalError = sqrt((Error1)^2 + (Error2)^2 + (ErrorN)^2...)

or in this case...

sqrt((10)^2 + (6.5)^2) = ~11.9

Then add in that E.S. is a lousy measure of consistency, mathematically speaking. It's easy to calculate and simple for the average person to understand, but it gives too much (all) weight to two 'outlier' data points - the ones statistically least likely to occur on a regular, repeatable basis - so the actual effect on target is (in my experience) rarely as drastic as predicted by simply plugging the high and low ES numbers into a ballistics program.

There's something to be said for considering absolute worst-case scenarios where you would experience the actual total ES spread between two sequential shots, stacked squarely against the absolute worst possible spread between shots in the group... if you like worrying yourself into a lather and an upset stomach

YMMV,

Monte

Monty .

I like good debates also and I am not offended buy your comments just because I can't shoot a 1
hole group at 1000 yards like you must be able to do because if you can ,then all you have to
do to shoot a perfect 1 hole group is to have a rifle capable of Zero MOA and a standard deviation
of .0000 and then shoot a perfect 1 hole group at 1000 yards and you will be the best there ever
was and the best there is!!!!!

I was shooting when you were still crapping in your britches and I can tell you that you have to add every variance to what the rifle would do in perfect conditions with no wind ,no mirage,perfect
temperature,perfect shooting position.zero SDs, perfect load densities, perfect brass and sizing
procedures,perfect bullets,And so on.

It is quite simple and Jethro math is all that's nessary "NO ONE IS PERFICT AND NEATHER IS
THERE EQUIPTMENT " or everyone would be shooting perfect 1 hole groups at 1000 yards
like you , so trying to flame me is a wast of time and you would be wise to spend your time
trying to convince others of your math skills and leave the shooting to those that can.

I was taught that the reason we have two ears and one mouth is that we are supposed to
listen twice as much as we talk in order to learn and I try to learn something every day and
don't spend time trying to flame everyone that I disagree with and spend the rest of my life
swimming is the shallow end of the gene pool.

J E CUSTOM

 

[milanuk]

Whoah there. Sorry if I came across wrong; thought it was fairly obvious I was joking with you a bit while trying to convey a technical point. For someone who is 'not offended' you sure seem a might stirred up. As far as that goes... for someone ticked off about being 'flamed' you're doing a heckuva job yourself. Keep it up, I love the 'britches' comments from you old-timers

You go on doing things the way that works for you and makes you happy. I'll keep on doing things the way that works for me - and learning, and hopefully, adapting - lord knows theres always plenty of room for improvement. Somewhere in between, I'm sure the world will keep turning and we'll all survive.

Later,

Monte

 

[AJ Peacock]

Ya know, I love discussions like this. By that sort of math, my gun would barely be able to hit the target, much less put 'em in the X-ring on anything resembling a consistent basis. gun)

Actually... errors don't stack linearly like that. In theory, they maybe *could*, but your chances are probably better of hitting the lottery. Root Sum of Squares (RSS) is a better method for figuring out how errors add up:

TotalError = sqrt((Error1)^2 + (Error2)^2 + (ErrorN)^2...)

or in this case...

sqrt((10)^2 + (6.5)^2) = ~11.9

Then add in that E.S. is a lousy measure of consistency, mathematically speaking. It's easy to calculate and simple for the average person to understand, but it gives too much (all) weight to two 'outlier' data points - the ones statistically least likely to occur on a regular, repeatable basis - so the actual effect on target is (in my experience) rarely as drastic as predicted by simply plugging the high and low ES numbers into a ballistics program.

There's something to be said for considering absolute worst-case scenarios where you would experience the actual total ES spread between two sequential shots, stacked squarely against the absolute worst possible spread between shots in the group... if you like worrying yourself into a lather and an upset stomach

YMMV,

Monte

Monte,

The RSS stuff works when you have a statistically large enough sample to be valid. Most guys shoot 5-6 rounds and calculate their ES from that. It's unlikely they have any true 'outliers' in their small sample, even if they do, the sample size is so small that we would never know it. With such small sample size, adding the error together is a much better (and easier) way to do it.

Think about it, if I shoot 5 rounds to get my ES, then I shoot a 5 shot group. I'll have a 1 in 25 chance with every shot to have a max+max situation (max ES induced vertical and max shooter/rifle induced vertical); I'll also have a 1 in 25 chance to have a min/min condition. If I shoot just a handful of groups, I will certainly hit those conditions. More likely, I'll have a situation that the velocity during a group is actually higher of lower than my sampled velocities! Especially considering that measurements are typically taken when the weather/temperature is nice and we shoot targets/game in all conditions!

In a perfect/mathematical world, we'd measure enough rounds to get statistically significant data, then the root sum of squares method would be the correct way to do it. We could calculate our confidence intervals etc. We could assess if the data (our velocities) falls in a normal distribution or not. But we don't shoot in a perfect world, and very few shooters record large enough data sets to do much more than ES and a simple SD.

AJ

 

[Boss Hoss]

I shoot 1K BR and if my ES is not 20 fps I will not waste my time but have used 25 fps before lol. Let me tell you this and I have won a few matches that you should spend more of your time learning to read the conditions than sweating the vertical dispersion difference at 1K if you have 2 groups of ten shots fired rapidly to simulate real conditions that have a ES of 25fps ---- you are in better shape than the majority of your competition!! I love it when people will tell me about how their rifle will put 3 shots into a .5 inch group at 100yds and then cannot get but a couple into a IBS 1K target out of 10.


Just remember that missing a 5mph condition change can cause you to go from getting wood to having a DQ.. Just my .02 here.

 

[canderson]

Thanks for the input from everyone. I just returned home from my first 1K shoot with this gun. I shot very well on the first three targets. 194,192,195 out of 200. The last relay, the wind was really switching and lettitng off. I did pretty good until the last six shots and dropped 7 points. Final score was 768/15x out of 800. I think I am getting just about everything out of the gun. Now, I just have to work on the operator. I think some more trigger time will help a lot.

Chris

 

[J E Custom]

Whoah there. Sorry if I came across wrong; thought it was fairly obvious I was joking with you a bit while trying to convey a technical point. For someone who is 'not offended' you sure seem a might stirred up. As far as that goes... for someone ticked off about being 'flamed' you're doing a heckuva job yourself. Keep it up, I love the 'britches' comments from you old-timers

You go on doing things the way that works for you and makes you happy. I'll keep on doing things the way that works for me - and learning, and hopefully, adapting - lord knows theres always plenty of room for improvement. Somewhere in between, I'm sure the world will keep turning and we'll all survive.

Later,

Monte

Monte.
I like your attitude and every now and then I have a bout of "Grumpy old man" and have to
eat a little crow.

I though it was a personal attack on my post and responded accordingly but it appears that we just disagree (Which is fine) so give an old timer some slack and except my apology for jumping
to conclusions.

I must be a personal friend of Murphy because strange stuff happens to me quite often so I
assume the worst and hope for the best.

J E CUSTOM