Accuracy or low ES?

[6.5x300]

Looking for some advice from the experts out there in developing a good moderate to long range (500-1000yrds) load. Just starting load development in a new barrel 300WM and I am asking the experts, do you guys go with the most accurate (smallest group on paper) or with the lowest ES/ED load for long range accuracy? Do you find that the lowest ES/ED load is always your most accurate load?

I am shooting a 28" CBI bull barrel 10 twist 300WM Match chamber on a Savage action in a Choate Tactical stock with Sightron SIII 32x glass. I am loading 190 grain match bullets (a discontinued Winchester 190 grain match bullet that matches the SMK 190) over RL-22 with Fed GM primers and WW brass.

At 200 yrds smallest 3 shot group is .675" at 3130FPS with the largest ES of 66. The smallest ES is 15 yet the group was the largest at 1.32" Seems a little strange that the smallest group is not also the smallest ES, and it seems strange that the smallest ES is the largest group?

My gut tells me to trust the accuracy on paper vs. what the chronograph says and I'm sure I could solve any challenges by simply testing two more loads at longer range, say 600 yrds but I only have 400 more rounds of these bullets and when they are gone they are gone, doesn't really do much good to chase the last few hairs of accuracy if I have no rounds left when done.

Anyway I'm curious what you guys have to add.

Good shooting and swage on!

BT

 

[MagnumManiac]

Looking for some advice from the experts out there in developing a good moderate to long range (500-1000yrds) load. Just starting load development in a new barrel 300WM and I am asking the experts, do you guys go with the most accurate (smallest group on paper) or with the lowest ES/ED load for long range accuracy? Do you find that the lowest ES/ED load is always your most accurate load?

I am shooting a 28" CBI bull barrel 10 twist 300WM Match chamber on a Savage action in a Choate Tactical stock with Sightron SIII 32x glass. I am loading 190 grain match bullets (a discontinued Winchester 190 grain match bullet that matches the SMK 190) over RL-22 with Fed GM primers and WW brass.

At 200 yrds smallest 3 shot group is .675" at 3130FPS with the largest ES of 66. The smallest ES is 15 yet the group was the largest at 1.32" Seems a little strange that the smallest group is not also the smallest ES, and it seems strange that the smallest ES is the largest group?

My gut tells me to trust the accuracy on paper vs. what the chronograph says and I'm sure I could solve any challenges by simply testing two more loads at longer range, say 600 yrds but I only have 400 more rounds of these bullets and when they are gone they are gone, doesn't really do much good to chase the last few hairs of accuracy if I have no rounds left when done.

Anyway I'm curious what you guys have to add.

Good shooting and swage on!

BT

Unfortunately, low ES/SD's aren't the full picture, because they may be stable in velocity, but will have different exit points in the whip of the barrel. Low ES/SD's don't guarantee an accurate result on target. I recall having an ES over 100fps in my 25-06 shooting 75gr HP's, but it printed little itty bitty groups, in fact it could shoot better than I could in the field.
I always go with the load that shoots the smallest groups and tune from there, even if the chrony results prove not optimal.
Rifles are a world unto themselves, no body has all the answers, as yet.

Cheers.
gun)

 

[6.5x300]

That's good to hear yet....... let's run some hypotheticals....... two different loads on paper at 100 yrds, one shoots .25" with 100FPS ES and the other prints a 1" group with 10FPS ES. How will these two loads shoot at 1,000 yrds? Which one will print a smaller group?

If ES wasn't even part of the equation and you can hold the same group size ratio out to 1000yrds (in a perfect environment, remember this is hypothetical) then you should get a 2.5" group and a 10" group right? but....... how much vertical spread will 100fps difference equal at 1000 yrds?

Just trying to get a better understanding, thanks for the help.

BT

 

[Ridgerunner665]

....... how much vertical spread will 100fps difference equal at 1000 yrds?

22 inches...or 2.1 MOA...thats with a high BC 7mm bullet compared at 2,775 fps and 2,875 fps.


To answer your original question...you gotta have both.

 

[6.5x300]

Just ran a quick JBM ballistic calculation on a simple 180 grain 30 cal bullet drop at 1000 yrds. A 100 FPS difference between 3000 and 3100fps equaled roughly 20" difference at 1000yrds.

So the numbers would suggest........

The 1" group at 100yrs with 10 ES should have a max group of 12" (10" plus the 10 ES difference of 2") at 1000 yrds.

The .25" group at 100 with the 100 ES should have a max group size of 22.5" (2.5" plus the 20" ES difference) at 1000 yrds

Of course this is in a perfect world with no other factors involved but???????

Does this make since? Am I to understand this correctly? It certainly is interesting and I look forward to what you guys have to add.

Thanks.

BT

 

[6.5x300]

Yep.... makes since I guess, got to have both. Posted my reply before I got to look at ridgerunner's, glad to see I was on the right track.

Thanks

BT

 

[J E Custom]

Foe short distances, I go for best the group.

For longer distances I want both As Ridgerunner said, with low ES/SDs you stand a better chance of having a more consistent group especially in the vertical group.

When I work up loads I try to get the lowest SDs and with the best powder primer combination found I then start working on case neck tension and seating depth to improve the accuracy and consistency.

J E CUSTOM

 

[MagnumManiac]

Your understanding and calculations are correct, vertical dispersion is your enemy at 1000yrds if you ES is way off, but, MoA at 100yrds does not mean MoA at 1000yrds, either.
I have experienced a load that was a little tighter in MoA at 600yrds over what it was at 300yrds, the groups are not smaller, it just prints into less MoA at the longer yardage.
The only way to find what shoots at range and what doesn't is to shoot at range, I use gongs on my farm, it is a challenge in the wind because I am in a large valley that swirls any air currents into bizarre patterns or no pattern at all. Wind may be from 12 o'clock at my bench, but may be at 3 o'clock at the gong, or vice versa.

Looking for a low ES/SD is the right direction, but you must have small groups that coincide with those results.

Cheers.
gun)

 

[6.5x300]

Thanks MM, posted my next reply here before I got to read the previous one again......

I suppose a question I need to ask or research too is "how many rounds does it take to accurately judge or predict the ES value?"

Can I accurately judge the ES numbers from only five rounds fired of a particular load? I am pretty confident I can judge the accuracy potential in the different loads with only one five shot group..... well.....I suppose the distance you shoot is going to make a difference too.........

Ok, just a simple question without going too deep then, how many rounds would you have to shoot to feel you have an accurate indication of the potential ES spread? I mean you could have a piece of brass with different neck tension, or any other number of factors that could send one bullet out of the entire lot down range at a different FPS throwing the whole ES calculation off, without firing enough rounds to notice the obvious "odd ball load" you might not ever notice???????

BT

 

[Ridgerunner665]

Can I accurately judge the ES numbers from only five rounds fired of a particular load? No...it takes at least 10, the more the better

I am pretty confident I can judge the accuracy potential in the different loads with only one five shot group..... very wrong

Answers in bold...

 

[6.5x300]

Yep I figured the more the better for everything. I knew the judgment of potential accuracy was going to be a deep subject, kind of why I let it taper off.

but in general, load development with a new gun or new barrel....... I researched the data then chose 5 loads from 70-75 grains with xx powder and bullet in one grain increments with five rounds per load shot at 200yrds. The 73 and 74 grain load showed potential, the group size was nearly 3" for the others while the 73 and 74grain load was not much more then 1". With that data I varied the loads by .3 grain increments starting with 72.7 up to 74.2 grains, each .3 grain increment loaded with 4 rounds this time for each load. The resulting loads and targets certainly showed a favorite and I was able to determine the 73.0 and 73.3 grain load showed the most potential. From there I varied the OAL from 3.4" to 3.60" (3.60" was a slight jam into the lands) and then determined the gun preferred 3.55" COL. I think that was a little over 60 rounds in finding the 73.0 grain load at 3.55 COL that went into a 3 shot .66" group, a called flyer opened it up slightly but still the accuracy of this load was obvious compared to the others.

I hope I didn't make it sound like I shot less then I did in the initial stages of determining a good load. Should I have done it differently?

BT

 

[coyotezapper]

Yep I figured the more the better for everything. I knew the judgment of potential accuracy was going to be a deep subject, kind of why I let it taper off.

but in general, load development with a new gun or new barrel....... I researched the data then chose 5 loads from 70-75 grains with xx powder and bullet in one grain increments with five rounds per load shot at 200yrds. The 73 and 74 grain load showed potential, the group size was nearly 3" for the others while the 73 and 74grain load was not much more then 1". With that data I varied the loads by .3 grain increments starting with 72.7 up to 74.2 grains, each .3 grain increment loaded with 4 rounds this time for each load. The resulting loads and targets certainly showed a favorite and I was able to determine the 73.0 and 73.3 grain load showed the most potential. From there I varied the OAL from 3.4" to 3.60" (3.60" was a slight jam into the lands) and then determined the gun preferred 3.55" COL. I think that was a little over 60 rounds in finding the 73.0 grain load at 3.55 COL that went into a 3 shot .66" group, a called flyer opened it up slightly but still the accuracy of this load was obvious compared to the others.

I hope I didn't make it sound like I shot less then I did in the initial stages of determining a good load. Should I have done it differently?

BT

No offense, but your load work up seems too random. Try this and pay attention to vertical in your groups and flat spots in your velocity.

Long range load development at 100 yards.

 

[dsculley]

The link provided by coyotezapper is a good one. It is a modified version of Dan Newberry's OCW method. You may want to check out Dan's site as well ( OCW Overview - Dan Newberry's OCW Load Development System ). He also has a forum here - Practical Riflery Forums... techniques and equipment of the practical rifleman... Forums if you are interested in learning more about his method.

While ES is easy to use, Standard Deviation is a much better predictor of performance. Of course, for SD to be meaningful, you really need more than 3 - 5 shots. 10 is a good starting point. A change in neck tension in one round, or a change in case volume in one round can give you a large ES, but the SD for the load may still be small. While we try to be as consistent as possible, we sometimes don't measure everything or we overlook a minor detail that shows up on the chrony and target. If we do this during load development it can lead to erroneous conclusions. I know that I have made my share of mistakes in this area.

Just my 2 cents.

Dennis

 

[dkhunt14]

I think that 100 fps is way to much spread for longrange. But I have seen where little groups at 100 and small ES is not always the most accurate group at longrange. Most benchrest 1000 yard shooters test at l000 because that is where they shoot. I had a 6 Dasher that would shoot 3 to 5 ES on the worst day and at 100 it would shoot under .250 at 100. At 1000 yards in competition it would never shoot under 13 inches. Another load where the ES was 10 to 12 would shoot in the 4 inch range. Now these are 10 shot groups. I have seen this on many guns. I never test under 400 yards anymore because when you go long it doesn't always hold out. At 400 vertical will start to show and it is hard to see it under that on a lot of different bullets and calibers The best would be low ES and great groups. I also look for the groups to be round. From all my testing the groups in decent conditions that were round stayed round all the way to 1000. If they strung up and down or vertically they usually didn't get better at distance. All this testing was done with 17 pound light guns and 80 pound heavy guns that are built with custom components and built to match specs. The guns were shot off of concrete benches with solid rests. Matt