es/sd standards

[ParallelCode]

Way I look at it, you need a systematic approach to hunt hobblins. I look at es/sd as a method to rule things out. So the question could be posited as, at what es/sd can you determine that it is not the cause of vertical dispersion and rule it out to confine the issue to other variables.

Well and concisely put!

 

[R Reed]

Well and concisely put!

Im trying, but trying to get my idea across has been hard. But i have to be able to identify when es/sd is a factor that has to be accounted for both in the es/sd numbers themselves or at what distances you can even determine that it is a measurable factor. In some cases, say 100yds, the vertical dispersion could be so small that it's hard to measure and correlate to any specific issue.

 

[ParallelCode]

Im trying, but trying to get my idea across has been hard. But i have to be able to identify when es/sd is a factor that has to be accounted for both in the es/sd numbers themselves or at what distances you can even determine that it is a measurable factor. In some cases, say 100yds, the vertical dispersion could be so small that it's hard to measure and correlate to any specific issue.

This has been a useful and interesting thread for me, I've learned some things. I'm glad you posted it.

 

[Okie_Poke]

There's little to say that hasn't been said, but I'm going to add my unqualified opinions.

I get emails from precision rifle blog from time to time, and find them to be interesting and sometimes informative. This is one that I saved. The guy does monte carlo simulations of group sizes at distance to see how various factors affect them. Consistent ammo velocity, expressed in SD, is one thing that he considers.

How Much Does It Matter? Overall Summary

As long-range shooters, we tend to obsess over every little detail. After all, we’re trying to hit r...

precisionrifleblog.com

ETA: I probably should have posted this issue, that was focused on SD:

How Much Does SD Matter?

As long-range shooters, we tend to obsess over every little detail. After all, we’re trying to hit r...

precisionrifleblog.com

I came here mostly to post this. I love Cal Zant's work over there. @Varminterror's thread on his ELR season last year was also top-notch.

Bryan Litz offered this bit in one of his books. I have the book at home, but I shamelessly stole this from the interwebs:

I'm not so much concerned at to what factors create or effect ES/SD, simply under what conditions ES/SD are a relevant factor, and what tolerances need to be held in those circumstances.

My very unscientific rule of thumb is:

• 0 - 300 yard - It doesn't matter
• 300 - 600 yards - It still doesn't really matter (I'm not shooting itty bitty targets) but I worry about it and control what I can control
• 600 yards + - It and everything else matters but I'm not reallyqualified to talk about this because I don't shoot these distances often enough

When I say I "worry about it and control what I can control," I mean I use brass of the same headstamp and bullets and powder from the same lot, I select an extruded powder and a match bullet, and I measure every powder charge using an RCBS Chargemaster Lite. My 10-shot SDs for bolt-gun ammo probably average about 10.

 

[Varminterror]

I'm not so much concerned at to what factors create or effect ES/SD, simply under what conditions ES/SD are a relevant factor, and what tolerances need to be held in those circumstances.

So the question could be posited as, at what es/sd can you determine that it is not the cause of vertical dispersion and rule it out to confine the issue to other variables.

Any distance where an RSS of compounding errors shows the total error is highly sensitive to velocity variability over the other factors, and/or where this sensitivity is larger error than tolerable by your target size.

 

[R Reed]

There's little to say that hasn't been said, but I'm going to add my unqualified opinions.


I came here mostly to post this. I love Cal Zant's work over there. @Varminterror's thread on his ELR season last year was also top-notch.

Bryan Litz offered this bit in one of his books. I have the book at home, but I shamelessly stole this from the interwebs:

View attachment 1261989



My very unscientific rule of thumb is:

• 0 - 300 yard - It doesn't matter
• 300 - 600 yards - It still doesn't really matter (I'm not shooting itty bitty targets) but I worry about it and control what I can control
• 600 yards + - It and everything else matters but I'm not reallyqualified to talk about this because I don't shoot these distances often enough

When I say I "worry about it and control what I can control," I mean I use brass of the same headstamp and bullets and powder from the same lot, I select an extruded powder and a match bullet, and I measure every powder charge using an RCBS Chargemaster Lite. My 10-shot SDs for bolt-gun ammo probably average about 10.

Which book, I found 2 so far. The applied ballistics, and the practical shooters guide. I'll wind up with both, but need to know which one that was in to start with.

 

[Varminterror]

Maybe I can answer this question the way I answer it for my own reloads:

I have chased this particular rabbit down both fruitful and non-fruitful trails for over 25 years. I have done so armed with incredible mentorship, appropriate analytical tools, and fantastic equipment.

For my competition ammo, I know achieving ~4-7SD’s is table fare, so I load to this level and live happy that for distances out to at least 1.6miles, I can demonstrate consistent control of my bullets, and the difference between 4 and 7 is nearly dissolved to nill. For my ELR loads, I may chase a repeating 7-8sd on 10 shot stings to try to shrink it to a 4-5, but at 4-5, I know I can’t do any more work to actually shrink that number.

Anneal, consistent necks, consistent volumes, good primers, strong striker spring and proper on fall, good fill ratio, lubed necks/bullets, proper neck tension, and I hit that 4-7 zone with exceptionally little effort.

 

[denton]

While I have great respect for Brian Litz, he will be the first to tell you that he is not a statistician. That leads me to believe that he does not know how standard deviations add, and I respectfully disagree with his table of suggested SDs.

As I said, I did run the math for excellent rifles at 500 yards, and my results were very different from some of the ideas posted earlier in the thread. I think what I'm showing here is a correct representation of reality. You can look at the results and decide for yourself what SD you need for the results you want.

Short version:

1. If you have an excellent bench rest rifle and have fully mastered it, and if you have perfected your ammunition reloading so that your MVs are identical, then under perfect shooting conditions you should get round groups.

2. If the standard deviation of your shot radius with perfect ammunition and conditions is +/-.125" at 100 yards, you will usually print .5" diameter groups at 100 yards and 2.5" groups at 500 yards.

3. If you then add variation in your muzzle velocity to the tune of an SD of 15 FPS (given the fairly typical conditions in the article), you will then print 500 yard groups that are 3.2" tall and 2.5" wide.

4. If you increase the variation in muzzle velocity to SD = 24 FPS, your 500 yard groups will be 4" tall by 2.5" wide. You would have to shoot very many samples to statistically detect this change.

5. Not fully developed in the article, but true: As you move to less precise rifles, the effect of MV variation will quickly diminish. As you go to even better rifles, it will become more important. If your rifle prints 1" groups at 100 yards, the effect of 24 FPS SD in MV at 100 or 500 yards will be practically undetectable. If you can shoot 1/4" groups at 100 yards, you probably want to get your MV SD somewhere below 15 FPS.

 

[JFrank]

This is ridiculous:

Alex was referring to my range mate Tom Mousel whose weekend aggregate was just out of this world, in fact tom is on quite a journey this year with his new ( 65 # ) rifle. I shot on every relay with tom all weekend. This year we’ve switched to HG first and LG second which means the wind is kicking up pretty good by then so light gun aggs will be down.

 

[JFrank]

The problem with placing too much value on SD/ES numbers is the fact that a well tuned rifle displaying positive compensation will hold its low vertical dispersion despite a higher SD.

 

[MEHavey]

well tuned rifle displaying positive compensation will hold its low vertical dispersion despite a higher SD.

Ordinary physics would tell the Gentle Reader that can't possibly be the case.
Higher/Lower initial velocities will produce correspondingly less/more drop in impact point at longer ranges.

 

[denton]

Ordinary physics would tell the Gentle Reader that can't possibly be the case.
Higher/Lower initial velocities will produce correspondingly less/more drop in impact point at longer ranges.

OK, at the risk of offending just about everyone..... MEHavey 21, JFrank 21, halftime.

What JFrank says about well tuned rifles is almost always true, because in a practical sense it is true of almost all rifles, well tuned or not. In fact, mediocre rifles show less effect from MV variation that superb rifles do.

What MEHavey says is also true, but for almost all situations, the effect is either undetectably small or close to it, for the reasons I gave earlier.

Unless you have a much better than .5 MOA rifle and are shooting at 500 yards or beyond, as long as the standard deviation of your MV is below 15-20 FPS, you will be very hard pressed to show that your MV variation matters.

 

[JFrank]

Just to throw one extra monkey wrench into the pile, the lowest es rarely translates to the smallest group. We have many many examples of the phenomenon.

Ordinary physics would tell the Gentle Reader that can't possibly be the case.
Higher/Lower initial velocities will produce correspondingly less/more drop in impact point at longer ranges.

And yet it is a truth.
For those with too much spare time and like to read. , research positive compensation.

 

[AJC1]

OK, at the risk of offending just about everyone..... MEHavey 21, JFrank 21, halftime.

What JFrank says about well tuned rifles is almost always true, because in a practical sense it is true of almost all rifles, well tuned or not. In fact, mediocre rifles show less effect from MV variation that superb rifles do.

What MEHavey says is also true, but for almost all situations, the effect is either undetectably small or close to it, for the reasons I gave earlier.

Unless you have a much better than .5 MOA rifle and are shooting at 500 yards or beyond, as long as the standard deviation of your MV is below 15-20 FPS, you will be very hard pressed to show that your MV variation matters.

It's weird we beat a subject to death but don't correlate it's significance to other factors. Is a 10fps vs a 15fps good enough to consider bullet sorting due to bc differences. Where does primer sorting come in. The small knobs seem a jumbled mess to me despite having a loose understanding what they all do. Need a dam flow chart

 

[JFrank]

OAL effects BC, bullet sorting or pointing for BC is most effective on 1000 yard target. Below that it’s just sorting for feel ( it makes you feel better)
I sort oal in .002 increments, primers I sort in gram mode at .002 increments because we’ve seen the effects of high weight against low weight on targets at 500 yards.

 

[JFrank]

A lot of this inside numbers stuff is above my pay grade, leading me to just rely on reading the target and not worry about the why and what if’s.

 

[GeoDudeFlorida]

Just to throw one extra monkey wrench into the pile, the lowest es rarely translates to the smallest group. We have many many examples of the phenomenon.

And yet it is a truth.
For those with too much spare time and like to read. , research positive compensation.

Ballistics is not entirely in the realm of ordinary physics. The assumptions in Newtonian physics are distractions in ballistics. Wind sheer, as just one example, is not necessarily strictly parallel to the ground.

Reading flags and observing the twinkle of spores in the breeze was always a little more than I wanted to deal with. Kudos to those who can do it.

 

[Varminterror]

I believe a major difference between any results Denton produces in this calculation and that which Litz presents is that we know Denton does not believe in a standard distribution of radius relative to centroid, whereas Litz has published empirical results to prove it does happen, which is built into the Monte Carlo simulator of WEZ tool. Inherently, this is a fundamental differentiator in how Denton would simulate group distribution.

 

[denton]

I believe a major difference between any results Denton produces in this calculation and that which Litz presents is that we know Denton does not believe in a standard distribution of radius relative to centroid, whereas Litz has published empirical results to prove it does happen, which is built into the Monte Carlo simulator of WEZ tool. Inherently, this is a fundamental differentiator in how Denton would simulate group distribution.

Wildly incorrect.

 

[MEHavey]

Someone (smarter than me * ) s`going to have to `splain to me how bullets fired from a barrel pointed in the same direction
will have the same vertical impact/dispersion vertically -- if their muzzle velocities are significantly different.



*I may be getting old, but I did sleep at a Holiday Inn Express some time ago -- (I just can't remember when )

 

[JFrank]

Someone (smarter than me * ) s`going to have to `splain to me how bullets fired from a barrel pointed in the same direction
will have the same vertical impact/dispersion vertically -- if their muzzle velocities are significantly different.



*I may be getting old, but I did sleep at a Holiday Inn Express some time ago -- (I just can't remember when )

It’s called positive compensation, here’s some discussion on the subject.

https://forum.accurateshooter.com/search/1364101/?q=Positive+Compensation&o=relevance

 

[Kaldor]

It’s called positive compensation, here’s some discussion on the subject.

https://forum.accurateshooter.com/search/1364101/?q=Positive+Compensation&o=relevance

And this why I'm a voracious reader of information, both good and bad. Learning something new, how and why it works or doesn't is something I strive to do everyday day.

I only have a passing knowledge of positive compensation but clearly I need to learn more.

 

[JFrank]

I’ll concede to the much smarter people to make heads and tails and why’s and why not’s.
I certainly won’t dispute any facts that say it doesn’t exist or does exist, I also understand those whom tune by the numbers.

I just follow the LR target.

 

[GeoDudeFlorida]

I’ll concede to the much smarter people to make heads and tails and why’s and why not’s.
I certainly won’t dispute any facts that say it doesn’t exist or does exist, I also understand those whom tune by the numbers.

I just follow the LR target.

Old shooting lore says the SMLE No.1 Rifles were considerably more accurate at long range (800m) with the bayonets mounted. The explanation is counterintuitive but the effect has been demonstrated.

I know. 800m isn’t really long range and old battle rifles are irrelevant to any discussion of accuracy. But it’s an interesting thing to consider when thinking about positive compensation, barrel harmonics and acceleration vs. twist effects.

 

[Walkalong]

People have pretty much proven that too large an ES/SD at long range will give a larger vertical than horizontal assuming either no wind or world class wind reading skills.

Yet this is true.

Unless you have a much better than .5 MOA rifle and are shooting at 500 yards or beyond, as long as the standard deviation of your MV is below 15-20 FPS, you will be very hard pressed to show that your MV variation matters.

And at 1000 yards the accepted norm is less. That said, we can screw it up with poor rifle handling, poor wind reading..........that part's easy enough.