ES & SD #'s & accuracy question **UPDATED 7-20-10**

[BigBamBoo]

Re: ES and SD #'s & accuracy question **UPDATED**

**UPDATE**
Ok...went out this afternoon in the 95+ degree temps with a new batch loads. Tried three different charge weights with BR-2 primers and three more groups with same powder charge but with Wolf primers.

First the Wolf primers shot a bit better for me. All groups shot at 300 yards.

Below are the two best groups...the left hand target is with the lower ES and SD #'s...ES 17 and SD 6. As you see...not a very good group.
The right hand target has a ES 39 and SD 16. I had the one called flier...the mariage was pretty bad...but out side of that all other 4 shots pretty much ended up in the same hole.

So...again...it seems this rifle does not like the low #'s....after reading all the links,etc., I am more confused then ever.

Take care,Stan

 

[JHardy]

Re: ES and SD #'s & accuracy question **UPDATED**

BBB:

It can get frustrating indeed. If the rifle shoots well, then it shoots, period. Having said that, I would do everything in my power to get an almost 40ES and 16SD down. It just is not acceptable at long range and will burn you badly. It just takes a lot of work at the loading bench.

But like another poster said, don't burn your barrel out testing.

Good luck,
Jim Hardy

 

[6BRinNZ]

Re: ES and SD #'s & accuracy question **UPDATED**

Hi Stan,

would you mind posting the actual chrony numbers?

 

[BigBamBoo]

Re: ES and SD #'s & accuracy question **UPDATED**

Right target:

1) 2943
2) 2969
3) 2982
4) 2956
5) 2982

HI 2982
LO 2943

AVG: 2966
ES 39
SD 16

Left Target:

1) 3020
2) 3004
3) 3006
4) 3015
5) 3003

HI 3020
LO 3003

AVG 3010

ES 17
SD 6

Take care,Stan

 

[RonAKA]

Re: ES and SD #'s & accuracy question **UPDATED**

I think I would first focus on finding the optimum velocity for your gun and load. I assume you are not changing bullet weight, powder type, or jam/jump? I would also settle on a primer. From what I see from what you have posted, the gun likes 2918 for vel, and possibly 2966, but not 3010. Have you considered doing a ladder test from 2900 fps to 3000 fps? If you tightly space loads between those two velocities, possibly 0.1 to 0.2 grains apart (one shot at each powder weight), and number each shot on the target as you step up in grains and velocity, then you can produce a plot of velocity on the x axis, and vertical position on the y axis. Hopefully you will find some flat spots where a few tenths of a grain make little difference in vertical position. That may lie between 2918 and 2966. The flat spots are areas where your gun load combination are "tolerant" to variation in velocity. Once you find those flat spots then focus on other things to see if you can minimize the SD and ES; Jump/Jam, neck tension, and primer type.

This article may be of some help. You have already narrowed down the range quite a bit, so you can go for a more selective range for testing now.

http://www.desertsharpshooters.com/manuals/incredload.pdf

One other thing to remember is that a chronograph will have some error, and typically they are said to be +/- 0.5%. That is +/- 15 fps or 30 ES at 3,000 fps. This suggests some of your low ES and SD numbers may be a bit misleading. Also a 5 shot string for doing a calculation is very small. I like to see in the range of 25 to provide meaningful SD's. Yes, I know, hard on the barrel.

 

[6BRinNZ]

Re: ES and SD #'s & accuracy question **UPDATED**

Hi Stan, I don't know a heck of a lot but my thoughts are below..

I think there are a couple of questions in this thread;

1./ why are the loads with high ES, SD at 100yrds grouping better than loads with low ES, SD - this is possibly due to ES SD having a smaller influence than other factors at 100yrds (if I interpret the comments ok)

2./ What should you do in order to get a good result at 1000yrds as you know high ES SD will hurt -

I have to admit that I wouldn't be happy with either group at 100yrds (the relative group size is approx the same so is one really any better than the other?), all the right hand group says to me is that I need to focus on removing the flyer, and I would focus on this group as it had the least vertical (assuming that is an onging pattern), chances are; the process of removing the flyer might also fix es and sd?

I guess the other point that crosses my mind, if you viewed these two groups at 1000yrds would you still be saying the one with the higher ES is the better group, the advise so far tends to suggest that it would have the greatest vertical in it...i.e. you may be better off to further tune the low ES, sd group.

having stated the above it needs to be put into context of the overall ladder test...and what that might be telling me for the next level of tuning.

 

[RonAKA]

Re: ES and SD #'s & accuracy question **UPDATED**

I believe the last two targets were for 300 yards. I'm seeing less than 1" vertical spread in the left target and less than 1/2" in the right target.

 

[6BRinNZ]

Re: ES and SD #'s & accuracy question **UPDATED**

Hi Ron,

yes I re-read and you are correct ( i would be stoked with this at 300), like I say I don't know a heck of a lot but I guess the points still stand? Happy for you to state otherwise as I am working through the process of group size vs ES SD as well at the mo.

 

[BigBamBoo]

Re: ES and SD #'s & accuracy question **UPDATED**

Thanks again folks for the input and guidance. I am not new to long range shooting. Just new to working with a chronograph. I have always just loaded for what shot best and had no means of checking #'s. This has served me well.

So I am going to load up the load that shows the best groups at 300 yards and shoot them in the 1000 yard match I am shooting in on Sat.
I will post results then. And if the #'s show lots of vertical at a grand I will re-visit my loads then and try for lower #'s.

6br....these groups where shot at 300 yards...not 100. If they were at 100 I would be still out working on loads!

I really am leery about getting to caught up in the whole # issue. This is a .243 so barrel life is already not it strong point. Again...the 1000 yard shoot should tell me/us what is going on. We will see.

And for those who are interested in the setup....probably not what most were thinking.

Take care,Stan

 

[RonAKA]

Re: ES and SD #'s & accuracy question **UPDATED**

Interesting that I had guessed .243 based on your velocities. I would put more stock at this point in the average velocities than in the ES and SD. Yes, I know the chronographs display them (as it is easy to do), but whether or not it is of value is questionable when the number of samples in the group is small.

On the other hand I can understand the value of a very tightly spaced ladder test in the velocity of interest. While each load may be different and essentially a sample of 1, this is of value because you are looking for a smoothed trend and flat spot areas.

 

[Steve Blair]

Re: ES and SD #'s & accuracy question **UPDATED**

I agree with you, Ron. After finding a likely candidate from 5-shot group load series, I load twenty-five rounds and fire a series of five groups. If I do not see consistency across all five, I dismiss it as a fluke and keep looking.

A chronograph can also serve the same role as a ladder test by analyzing velocity results. Notice the Sierra velocity flattening at 33.9 to 34.0 grains. Later testing showed the range as 33.8 to 34.0. I am now shooting the load at 34.0 RL17. It takes an 8" drop tube to get that much into a 6BR case but I get just over 3000 fps with no overt pressure indications.

 

[camac]

Re: ES and SD #'s & accuracy question **UPDATED**

. I would put more stock at this point in the average velocities than in the ES and SD. Yes, I know the chronographs display them (as it is easy to do), but whether or not it is of value is questionable when the number of samples in the group is small.

On the other hand I can understand the value of a very tightly spaced ladder test in the velocity of interest. While each load may be different and essentially a sample of 1, this is of value because you are looking for a smoothed trend and flat spot areas.

This is the core thing. Under 300 yards it is far more critical to get the load right so you are in the accuracy node. Map those velocities versus shot placement as much as possible. Ignore the horizontal at this stage for your load development.
What you are clearly seeing is results of barrel vibrations at different accuracy nodes, and has very little to do with ES/SD. They come into play further out.

Once you know your accuracy nodes and are ready to move out to further distances then you start on the other ES/SD improving stuff.

The basics are well documented on this site but are basically mostly in your brass prep.
1) Clean your shells, Trim and chamfer your cases.
2) then weight sort them (one off, simple and quick method to help).
3) Uniform your primer pockets and holes (also a one off step that will help immensely depending on your brass brand and batch. - Discard any oversize primer holes or use them for hunting etc.) get a pin vise and either 4/0 or 5/0 tapered pin reamer with a depth stop or other such suitable size drill bit. Do not overdo it. Typically 78-82 thou ( I think but I use the taper to do it so can't measure accurately) for large flashole sizes
5) Accurate powder charges (ensure accurate loading +/-0.1 grain in a 243 is also 13-15 fps)
4) experiment with neck size and seating depth (AKA neck tension and this is one that takes a lot more range time and bullets but can really cut down the ES. e.g. same load in my 6.5* 284 with two seating depths (10 thou jam vs 80 thou jump) can change ES from 18-20 up to 70-80.

6) Primer/powder combination trials

The are pretty much the golden rules and will make a difference (May have forgotten something as trying to mash this together quickly but feel free to add anything guys). They will also take a very long time to get through all the trialling so you can shortcut this by asking a few others what they are using for primers/ powders / bullets etc, or go to the main page here.

The final things to do (once you get bored with above!!)
are sorting bullets on bearing surface length , meplat etc., Annealing, and neck turning etc etc.

But as Ron also suggested , most chronos have an error of +/- 0.5 % or around 30 fps so use it as a relative tool for you only. Personally I think they are generally much more accurate on a shot to shot basis but most of the error comes in the actual speed and every time you take it out and reset it up.

 

[Rust]

Re: ES and SD #'s & accuracy question **UPDATED**

Seems like everyone is overlooking the obvious as to why the velocity of 2966 (Av) is producing more accuracy. Simply put, it is very close to or right on top of a null point in barrel vibration.

About a year back or so, Varmint Al posted what is probably the best analysis of barrel vibration and how it affects accuracy and even can compensate to some degree for velocity variations, at least at closer ranges, I've ever seen. If it isn't here try his sight a VarmintAl.com.

But as the range really starts to stretch, the velocity spreads will show increasing vertical dispersion.

Work on decreasing ES/SD at the velocity where your best accuracy is. Plenty of suggestions have been posted but to keep it simple start with the simple stuff first.

1. Uniform cases. Fired and sized the same number of times. Primer pocket depth uniform. Primer flash holes centered in the case and uniform diameter.

2. Uniform powder charges within .1 gr.

3. Uniform bullet seating depth. Vary this from seated into the lands to seated off the lands to see what impact it has on your numbers.

Keep in mind most rifles have a nice barrel null at or right around 2950 fps and it would appear yours is no exception.

 

[BigBamBoo]

Re: ES and SD #'s & accuracy question **UPDATED**

Thanks again gents. Lots of info here.
I do do some basic case prep. I do not neck turn. I do weigh my brass (Lapua) and sort my bullets for ogive.
I measure my powder and do not use a powder thrower (I use a RSBS ChargeMaster).

I will keep posting updates.

Take care,Stan

 

[JHardy]

Re: ES and SD #'s & accuracy question **UPDATED**

BBB:

"I use the RCBS ChargeMaster . . ." Depending on how you use it, that could be part of the high ES/SD numbers. I use the ChargeMaster as well. I set the ChargeMaster to throw the charge I want. It is usually under. I then take that pan of powder and dump it into the pan on a very accurate digital scale that measures to .02 grains. To the best of my ability, I load the case to one kernel of powder. The ChargeMaster is great, but it will hit you with a .5+ deviation sometimes -- that is enough to throw ES and SD out the window.

I guess the bottom line is that deviations in powder charges will change your ES/SD more than anything else.

Please excuse if you use the ChargeMaster in this way as well, but I thought I would give you a heads-up just in case you were relying JUST on the ChargeMaster.

Regards,
Jim Hardy

 

[Steve Blair]

Re: ES and SD #'s & accuracy question **UPDATED**

Jim,
I use the Chargemaster and Acculab VIC 123 the same way but with the Chargemaster set to .1 grain under, then trickling on the Acculab. I try as much as possible to hit weight exactly. Some fine kernel powders, like 8208 XBR or H322, are easy. Denser, larger kernel powders like Reloder 17 mean that I usually settle for ±.02 grain. Using this technique and others described here, I've found a number of loads with single-digit ES. It is not rocket science but it does take some effort.

 

[camac]

Re: ES and SD #'s & accuracy question **UPDATED**

I also have a set of accurate lab (0.001 grams) scales and use powder thower into pan (usually within 0.2 grains then trickle the same as you guys. It did make a big difference but the scales were very expensive (luckily I had a lab back then to buy them for) - The acculabs are over $300.00 too so not cheap.

To put this in perspective for BBB: +/-0.25 grains (0.5gr deviation as you said Jim)= approximately 30-40 fps in the 243.
+/-0.1gr (just because a scale measures to 0.1gr doesn't mean it will give that accuracy to you though)= around 15fps
+/-0.02 grains = around 3 fps!
To put this into further perspective a 115gr DTAC doing 2930fps will be over 9 inches lower than one doing 2970 (nearly 1 full moa vertical on velocity alone). a 107 gr sierra MK doing same will be nearly 11 inches.


You need to decide what range you are going to shoot at and how much to spend on scales.
If you want to shoot 1000yds 30-40fps will hurt.

For 1000yd If you have the money I would recommend you buy an acculab and set up like these guys, if you don't have the dough sell the chargemaster and use money towards acculab and throw from scales into pan and trickle as close as you can. With fine digital scales you also need :- solid benches, no breeze (fans or airconditioning as well), shields or hoods and accurate calibrating before and after each set of loading is advised.

Oohh it never ends..

 

[camac]

Re: ES and SD #'s & accuracy question **UPDATED**

Just to put this in further perspective. There is an old saying in benchrest. "It is the sum of all the little things" that make the difference.

Imagine in this case where you didn't control all the above factors. Once every now and then you get a loaded round that has: a small flashole plus a low powder charge plus less neck tension (etc etc). This is the bullet that can have 100fps+ lower velocity. The chances are low of them all happening together but shoot anough and they will. This is Extreme Spread. The less you control all the variables, the worse this can be.
It is multiplicative!

Someone that controls all the variables above well might only have 3-4 fps from each variable. 5 shots through a chrony will show very tight spread and low SD (usuall single figures). Shoot 100 through chrony and the ES might get out to 15-20fps or so.
Not controlled as tightly and 100 shots through chrony with 30-40 fps from powder, same from flashole and same from neck tension/seating depth plus others can end up with one or two really extreme velocity spreads. This just doesn't work well at long range. You will here it often standing behind the firing line "where did that one come from".

 

[TonyR]

Re: ES and SD #'s & accuracy question **UPDATED**

I should be so lucky that I am only wondering about one! Great discussion and lots of good insights.

 

[BigBamBoo]

Re: ES and SD #'s & accuracy question **UPDATED**

Ok...so I shot in the 1000 yard match (NBRSA) this last Sat. and here are my targets. Can you tell the wind was blowing!?!? I ended up taking 3rd place and my best group was right at 6 1/2".
So maybe someone can tell more from these pics, but out side of the random bad call,mirage (about 95 deg.),wind shot...most shots are lateral and not a whole bunch or vert. going on?? Did I mention it was windy? ???

Take care,Stan

PS...this is the first time I have shot this rifle and loads to 1000 yards.