Thread: HOW IMPORTANT IS ES

What would be interesting is whether SD can give you an indication of a wearing barrel. The stag barrel is brand new while the Pattern 1914 is 100 years old. yet more things to experiment with.

SD will give a better idea of how consistent/repeatable your ammo is. ES just gives the highest and lowest velocities.
Consider these two imaginary 5 shot strings

3000, 3000, 3000, 3000, 3020

3000, 3005, 3010, 3015, 3020

Both have the same ES, but the first one will have a lower SD

The Q would be is there a noticable improvement in grouping between the two? if not then ES maybe the better measure, if yes then the SD is surely? Next time I intend to take an old digital camera up and record the shots as they arrive, just have to hope the battery is still OK and no idiot shoots it...and that includes me, LOL the nasty is the shrapnel when others are wacking steel plates.

Originally Posted by steven

The Q would be is there a noticable improvement in grouping between the two? if not then ES maybe the better measure, if yes then the SD is surely? Next time I intend to take an old digital camera up and record the shots as they arrive, just have to hope the battery is still OK and no idiot shoots it...and that includes me, LOL the nasty is the shrapnel when others are wacking steel plates.

If I had to choose between those two hyperthetical strings to progress fwd with my load development, keeping in mind that such small samples are statistically suss, I would choose the first one and try to explain why 1 shot was out from the others. Could be many reasons. Groups at that stage could be less than perfect despite low ES and favourable SD. Time to frig with seating depth. Yeh, seeing your shot fall at say 500yds (must move out to at least that range once happyish at 100yds, but probably 250 for hunting type conditions) needs to be recorded in order against your brass fired. Also keeping your brass once fired in your box in order. Have seen guys trying to do serious long range load development arrive on the mound and tip a whole lot of loaded ammo out of a plastic bag on to the grass! And once fired they are all returned to the bag, assuming none got lost. Seems they are a few of use building camera systems right now similar to 7mmsaum's.

OK, another of my "$0.02c".

I am relatively new to shooting, hunting and reloading but however i don't have much experience i do "research" A LOT.
In my understand, and what i think i learn with my research regards SD and ES are:

SD - is "somehow in MY understand" the "measurement or estimation" of how much the bullet vary from a "straight line" as it exit the muzzle of your rifle or pistol, saying it, i can not confirm if it is real or not or how it is measured during the process, but, as we all(or many of us here) talk about "concentricity" and "bullet alignment" during the seating process i think it is how they "ballisticians" "calculate or estimate how "far" the bullet path is from a "straight" line, if the bullet is seated not "centred" enough the path will be "unknown" with the POI varying with a higher "off alignment". So, if you shooting at long ranges it will affect your accuracy.

ES - is in my understand the measurement of "how consistent" your bullet velocity will be so it will "hit" closest to the "centre" or point of aim. If any of you guys watch Brian Litz videos i am sure you will find some more "technical" info there and with a lot more "quality" than my own "findings". the lesser is the speed variation the less chance the projectile will hit away of the centre.

Well, i think i wrote too much so i will stop here with a quick "conclusion". The smaller are the numbers achieved in SD and ES the better it will be(or should be), however other factors can and will contribute to the final "accuracy" with examples such, bullet seating depth, max velocity, case capacity, etc, etc, etc. so, if you really want to compete in F-Class and its variables or bench rest match you may need to "study" in depth all of these variables.

I hope it help a bit and i apologise if i wrote some or a lot of "BS" but as i said, it is only my understand. If someone here can clarify more or correct me please do it.

Thank you for your time.

Mac

SD is standard deviation, a mathematical calculation of how far away from the mean the results are. (I think) 1 standard deviation is +/- 34.1% away from the mean. ie 66.2% of results are within +/- 1 SD of the mean.

Originally Posted by stug

SD is standard deviation, a mathematical calculation of how far away from the mean the results are. (I think) 1 standard deviation is +/- 34.1% away from the mean. ie 66.2% of results are within +/- 1 SD of the mean.

68.2%, but yes.
SD being the stuff in dark blue (the most common distribution), with ES being the shots at extreme ends of the scale:

OK, just another little "fixing" trying to make easy to understand.

SD can be how far the projectile will deviate from the POA because the speed variation. the higher is the ES the higher will be the SD to the POA. A projectile flying at 2900ft//s will "theoretically" hit a target at 800 metres "bulls eye", if the next projectile has a estimated velocity of 2800ft/s it will hit the target at maybe 2" low. from this "example" you/we can try to figure out what we trying to understand regards "SD and ES", the more consistency we have the more "accurate" it will be, or should be.

Sorry again for more "crap".

Mac

Hi, I've tried to put down an explanation of SD and ES. http://www.nzhuntingandshooting.co.n...t-es-sd-22402/
Hope it helps a bit.

The effect of a given ES can be found for both drop and susceptibility to drift from wind by feeding the two extreme values into a exterior ballistics program and comparing the outputs at the range of interest. As to a link between accuracy and variation in muzzle velocity I agree with the other replies and treat them as independent and the effects as additive.

Yes, all very interesting but overly complicated.

A fair summary might be:
SD- How consistent are my velocities on average?
ES- What are the worst case velocity variations?

(PS. I used to tutor in stats)