Small ES and SD But !!!!

[Okiecat]

I'm not new to reloading but now I'm into the 1000yd game. I tested 5 loads today and had one go ES 3 & SD 1.4. This was only 4 shots @ 300yds and the group was one of the biggest??? What do I do now? Nearly all the others were running es in the 40's and sd in the 20 range.

 

[aJR]

Hi Okiecat, I have not used a chrono to develope L/R Benchrest loads for some 8 years now..Everytime i included a chrono in the end quest of "small groups" it took longer to get there,more rounds were fired and i found exactly what you have ..The smallest group contradicts what the chrono said would be the best..They are great for finding if you have enough speed to do the job at hand but..JR..Jeff Rogers .just MO

 

[Okiecat]

Thanks J.R. I agree on the too much shooting just groups. But my best load is 100 to 130 fps slower than alot of the rest that are shooting this. Oh its a 22-243 with 80grainers. I just thought that maybe I should play with this new powder and work on the jam on the bullet.??

 

[jb77]

Okiecat, there have been so many accuracy tests done where the most accurate groups did not have anywhere near the smallest ES or SD. I wouldn't worry about it. We were shooting small groups before chronos were widely available to measure and torment us with ES.

I will say there are a lot of individuals on this site that are perfectionists and will strive to get the numbers as low as possible so as to be as consistent as possible.

If I found a load and it was consistently accurate at the range that you are going to be using at, then I personally wouldn't care what the ES and SD are.

 

[wnroscoe]

In the short range BR Game, some of the best groups have the highest ES & SD numbers, dont know why. Like you, I've had ES & SD #'s in the 1's & 2's but, the groups measured in inches at 100 yards :lol:. I now test with out the chrono and judge by group size and shape. I chrono after just for the average velocity for my "estimated" sight adjustments at long range.

 

[TominSWNY]

I have had two different 3 shot patterns with 0ES and 0SD. Just kept on marching in search of a group and the the heck with the numbers. Avg velocity is handy for clicking in the first shot at 600 yards when you only have a 100 yd range to work with.

 

[AlNyhus]

The biggest reason that not all low ES/SD loads group well is actually pretty simple: the barrels muzzle isn't in the same position when the bullet clears the muzzle due to the barrels vibrational pattern.

Barrel vibrational characteristics are individual to each barrel and are influenced by many, many things: bedding, reciever to barrel thread fit, barrel to reciever face fit, bolt to reciever clearance...all of these things play a part. Now add to that the different vibrational signals the barrel sees from different powders, bullets with different shank lengths and varying diameters and you start to get an idea why some loads with great numbers don't always group so well 'on target'.

Don't get me wrong...I think it's great when you get accuracy and low ES/SD numbers to coincide, no matter what yardages you're shooting at.

The one thing to remember about plopping in different velocity numbers and coming up with the 'on target' vertical that you theoretically get is that these programs assume the muzzle is in a fixed position...which of course is impossible due to vibration.

Good shootin'. -Al

 

[memilanuk]

okiecat,

Basically, four shots is too little to accurately determine whether the load is 'good' or not based on ES/SD - you might have lucked on a handful of random shots that happened to fall near each other in terms of chrono readings. On the other hand, as you observed, you can tell if the load is 'bad' in very few shots... if it ain't grouping tight by four shots, it certainly isn't going to group any *better* with more shots downrange.

You might find the following link of interest:

Statistics for Rifle Shooters

 

[AlNyhus]

Lynn:

I think the work being done with tuners, tensioned barrels, etc. is very interesting and has a lot of potential. As to whether or not Mr. Calfee is correct in his assumptions on being able to stop the muzzles movement...well, it certainly seems to have worked in the rimfire BR world, that's for sure. Whether or not this is directly applicable to centerfire BR remains to be proven. Hopefully the rules in traditional 100-300 BR will be relaxed a bit in the future to allow more experimentation in this area. I know I'd love to tinker with this, but since at this time it's outside the current rules for the classes I compete in, it's hard to make a case for spending any time with it at this point.

But this is probably starting to stray a bit from the posters original question, I suppose.

Good shootin'. -Al

 

[aJR]

Guys, One of the things noticeable about big tension barrel systems is that the powder charge amount has way less effect on groups than you would think ..If you have a powder that will burn clean,i change powders if it's filthy regardless of initial groups)then in my gun the groups don't vary much when changing from say 72gns of vv560 through to 78 gns all the while varing the seating depth from ten in to ten out..They do climb up the paper as the charge is increased but don't have large changes in size like when you remove the tube.. Having said that there is a place in the tune that the vertical dispersion comes together at long range,i beleve this has to do with the powder being in the perfect combustion cycle and the fact that my set up still retains some compensation effects unlike the giant stretched/water filled units.. I also believe that untuned barrel's whether that be by fixed form,tensioner) or the adjustable muzzle type is quite often seeing the powder fight the barrel vibrations for which is going to be dominant.. Sometimes this can be overcome by real high pressures that most don't ever want to go to..The reason i have stayed with the Stretched barrel is that it's fixed,i would not be able to stop tweeking the adj unit in an effort to get the best in all conditions..If i had to say the one thing that make my set up worth the effort is that when the weather changes in either temp or humidity or both by a large amount then i don't see a great drop off in the group size, especially over a two day event..JR..Jeff Rogers

 

[Okiecat]

Well thanks to everybody. Man there are some really sharp people out there. I guess I was kind of trying to ask what steps to take to lower the es. Isn't the velocity of a bullet controlled by the varibles of the components and how they are assembled. Ex: powder amounts, bullet depth,primer change. ect..

 

[Marksman]

This thread has been a great read and answered some of my own questions. A few weekends ago I was testing loads for my 6mmAI and I had one group turn out to have an ES of 4, with an SD of 2, and oddly enough, it too was the worst shooting group. I ended up settling on a load that had an ES of 25 and a SD of 13.

 

[TonyZ]

Lynn, having now built a number of rifles with tensioned tubes and having sat beside a few in competition over the years, i believe that the tensioned system that we employ has more to do with muzzle positional location shot to shot from a purely structural aspect and very little to do with "tuning" or "damping'. Just the very simple point that no amount of lock nut adjustment or preloading shows up as a "tuneable variable" within the tensioned barrel arrangement indicates this clearly. From an engineering view, the tube strengthens a flexible arrangement of barrel abuttment to an action face and do firmly believe that the larger section diameter the tube has, the more stable the muzzle becomes. In saying that, too large a tube diameter may have a detrimental effect where the compensation associated with the less than desirable ES and SDs is still able to produce a tight group vertically at 1K with a more "flexible" setup. As does JRs. I believe there is a limit here, but cannot explain the past results of Charles Bailey other than by saying that a very motionless muzzle in a very stiff arrangement,six inch tube i believe) can shoot well at 1K when the ES is in the single figures. Compensation in a tube of this dimension would most likely not exist and to many the notion that compensation exists in the first place is a topic of hot debate.
As for ES and SD, when someone comes up with a chrono that has no ES or SD in itself, then i may take a little more notice of them.

 

[AlNyhus]

TonyZ:

You bring up a great point regarding chronograph numbers. Virtually all chronos have an error factor as stated by the manufacturer...usually around 1%. When a shooter tests a 3,000 fps cartridge over a chono, the chonograph has a 30 fps. possible margin of error 'built in' to it. So, when people get all warm and fuzzy about single digit ES/SD numbers they are really not coming to the next logical conclusion regarding what the chrono is telling them.

I've shot those single digit ES/SD numbers over my chono..but I know that what I'm actually seeing is that my ES/SD's are outside of my chonos ability to register under that 1% error factor. When my 30WolfPup @ 3140 fps shows a E.S. of 12 fps for a five shot string, I know that in reality it's simply under 31 fps. and not exactly 12 fps, for example.

This isn't exactly a popular fact among those that live and die by their ES/SD numbers, though.

 

[reverend]

I sure you probably know this but if a manufacturers measurement tolerances are + or - 1% and the velocity is 3000 fps, + 30 fps and - 30 fps, a measured difference of 60 fps could be the same speed.

John

 

[jb77]

Thank you Al, this is a great post. My question is when does all of this just become too much?

I am really amazed at some of the tiny groups shot at long ranges but this goes somewhat to the root of why it is hard to attract new shooters to our sport.

Could you imagine being a new shooter and never having been to an unlimited match and reading this post?

It is an amazing topic though.

 

[tripcrow]

Just exactly is meant when we say a crony has a 1% margin of error? If you read the article milanuk linked to you’ll see a 50 shot group with an ES of 46fps while doing 2988fps avg. That’s under the +/- 1% error margin before even taking into account shot variation over 50 shots. So doesn’t that 1% error mean that the 2988fps is off of the group’s real average velocity up to a possible 1%? But the crony is reading off the same base error amount consistently, say 30fps slower than it’s really doing, for each shot? Obviously it can’t be off its base error by 1% every shot and come up with an ES of 46fps over 50 shots.

 

[tripcrow]

So the error is mostly in the ability of a crony to read the precise actual speed. Say like a cloud will make it read +/- 50fps. Not in its ability to display consistencies or inconsistencies between shots when all other things are the same?

But if I’m load testing and looking for SD or looking for velocity nodes with a fresh keg it doesn’t matter much to me if my crony is off 1%. Just as long as it’s off the same error for every shot. No?

 

[AlNyhus]

Seems we're stuck with the theory that there's a built in 1% error.

Respectfully, the error factor is not a theory..it's a fact substantiated by the various makers of chonographs.

That certainly doesn't diminish the valuable info we get from a chrono, but I think we have to put that info in the proper perspective. This is no slam against any of the excellent chonographs available today..shooters of years past would have given a large portion of their anatomy to have access to the units we're discussing.

Basically, here's my point:
-Chronographs have an error margin..usually around 1%
-When we get ES/SD numbers outside of the manufacturers stated ability of that unit to deliver reliable info, we need to question those numbers.

Let's take the example of a 3,000 fps. reading in a unit with a 1% error factor, for example...'cuz it's easier for a simple dirt clod like me to do the math with even numbers. :thumb: Let's say that unit gives us ES/SD numbers of 10 with our 3,000 fps. cartridge:

-Velocity: 3,000 fps
-Possible error: 30 fps
-ES/SD numbers: 10 fps,1/3rd the units error factor)

So, how can we say with absolute certainty that our ES/SD numbers are exactly 10?

My reasoning is that the ES/SD...while under 30,the units ability to measure as stated by the mfg)...is unlikey to be exactly 10. It could be 29. Or 4. Or anything between 0 and 30. But not exactly 10 since the unit is not sensitive enough to recognize deviations of less than 30.

Good shootin' -Al

 

[AlNyhus]

dmoran: Thanks for taking the time to dig up and post Henry Child's comparative testing on those chronographs. I've always enjoyed Henry's posts on his testing and this one was, to me, one of the most informative. Too bad he has quit posting....I'm sure the time constraints involved with answering all the questions must have been huge.

But this test doesn't answer or address what seems to trouble people the most. And that is: "What's the error factor in my chronograph?"

For those interested, I would suggest they simply call the makers of the different chronos they are interested in and ask them this question: "What kind of accuracy do you guarantee?". Then use this info to decide what unit best fits your needs as a shooter.

Over the last few years, I've noticed that when the subject of chronos comes up, shooters are divided into two camps:

#1 Shooters that recognize that the chrono is a very useful tool, within the limitations of the unit. They get some basic 'meat and potatoes' info from the chrono but let the target be the final deciding factor on what loads are good or bad.

#2 Shooters that live and die chrono numbers. If the chrono says it..it's law. End of story..done, finished. No room for discussion.

Like a lot of things in shooting..if you think something works for you, it probably will. If you think something doesn't work, it probably won't.

On some boards the name calling and mud slinging would have already been pretty nasty by this point. It's nice to be able to offer widely differing opinions in a civil manner while still being open minded enough to look at things from the other persons perspective.

Happy Thanksgiving! -Al