Group size vs SD/ES

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laker415

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So I'm curious what you guys are more worried about when it comes to dialing in a load for distance shooting. I'm just starting to play around with neck tensions and also starting to shoot at longer distances. Currently I'm narrowing down a load for the 175 Sierra matchking in my 308.

I just shot 2 groups at 200 yards. One group was just over an inch for 5 shots with an SD of 10 and an ES of 27.

The other group was around 1.5" for 5 shots with an SD of 7 and an ES of 18.

What would you guys do? Perhaps I'm over thinking this. I have just been reading on how your ES becomes more of an issue at distance. Thoughts? Thanks
 
I'm curious about this too.

I load test at 200M and many times the best group does not have the best SD/ES numbers.

In theory smaller SD/ES will be an asset as distance increases but is it worth taking the loads with better ES/DS numbers over those which group better?

To date I have continued with the load that grouped best and it seemed to serve me well but this may be an illusion as I did not test the loads with low ES/DS numbers at much longer ranges for comparison.
 
Sniffer said:
I'm curious about this too.

I load test at 200M and many times the best group does not have the best SD/ES numbers.

In theory smaller SD/ES will be an asset as distance increases but is it worth taking the loads with better ES/DS numbers over those which group better?

To date I have continued with the load that grouped best and it seemed to serve me well but this may be an illusion as I did not test the loads with low ES/DS numbers at much longer ranges for comparison.
Click to expand...

Well I just reloaded 40 rounds of the combo with the slightly higher ES and SD. I want to shoot 10 at 300 for that group challenge and see. It is showing as quite accurate as is.

I will focus on improvements with that load to lower es and sd. Getting a salt bath annealing setup and switching to Lapua brass should help.....I hope. Also looking at addressing my current powder dispenser and upgrading to something more trustworthy
 
laker415 said:
So I'm curious what you guys are more worried about when it comes to dialing in a load for distance shooting. I'm just starting to play around with neck tensions and also starting to shoot at longer distances. Currently I'm narrowing down a load for the 175 Sierra matchking in my 308.

I just shot 2 groups at 200 yards. One group was just over an inch for 5 shots with an SD of 10 and an ES of 27.

The other group was around 1.5" for 5 shots with an SD of 7 and an ES of 18.

What would you guys do? Perhaps I'm over thinking this. I have just been reading on how your ES becomes more of an issue at distance. Thoughts? Thanks
Click to expand...

Two five shot groups is a small sample for group size and I’d try them again shooting the groups round robin. It only takes a breath of a wind change to go from just over an inch to 1.5” at 200 yards.

Either way those SD/ES numbers are pretty good for non-premium brass, no annealing, and powder measured +/- 0.1 grain so I’d take whichever is faster and more precise.
 
rgv said:
Two five shot groups is a small sample for group size and I’d try them again shooting the groups round robin. It only takes a breath of a wind change to go from just over an inch to 1.5” at 200 yards.

Either way those SD/ES numbers are pretty good for non-premium brass, no annealing, and powder measured +/- 0.1 grain so I’d take whichever is faster and more precise.
Click to expand...

Thanks for the reply. I'm going to shoot some farther groups, 10 rounds minimum and see what the chrono says
 
Sniffer said:
I'm curious about this too.

I load test at 200M and many times the best group does not have the best SD/ES numbers.

In theory smaller SD/ES will be an asset as distance increases but is it worth taking the loads with better ES/DS numbers over those which group better?

To date I have continued with the load that grouped best and it seemed to serve me well but this may be an illusion as I did not test the loads with low ES/DS numbers at much longer ranges for comparison.
Click to expand...

Definitely compare the two loads... it will be very enlightening.

Short answer, the best grouping loads at long range is the best load to use.

No one scores your chronie print outs.

Jerry
 
Mystic Precision said:
Definitely compare the two loads... it will be very enlightening.

Short answer, the best grouping loads at long range is the best load to use.

No one scores your chronie print outs.

Jerry
Click to expand...

Now I'm intrigued.....:d

I am going to load up a handful of the load that gave incredible SD/ES numbers and see what happens. It is only 0.3gr different.

I'm pretty happy with how the other load groups and I'll be surprised if I find something better.
 
I’m curious about this too. From my readings it’s my understanding that once you’ve found the velocity window that your barrel / bullet combination likes, there is some margin for error while keeping accuracy.
 
Do you weight sort your brass? This isn't the most accurate way to sort brass, but who has time to sort several hundred/thousand pieces of brass by volume? I sort brass by weight into .5 gr batches. Most people shooting long range are using powder scales that will weigh .02 gr of powder. Shoot for groups and don't worry too much about the chrony numbers.
 
Sniffer said:
Now I'm intrigued.....:d

I am going to load up a handful of the load that gave incredible SD/ES numbers and see what happens. It is only 0.3gr different.

I'm pretty happy with how the other load groups and I'll be surprised if I find something better.
Click to expand...

Come on down and we can test out to 700yds. You will learn alot

Jerry
 
Tikka223 said:
I’m curious about this too. From my readings it’s my understanding that once you’ve found the velocity window that your barrel / bullet combination likes, there is some margin for error while keeping accuracy.
Click to expand...

Define "window" and "accuracy"... the less demanding, the wider both are. When you are concerned with the highest levels of performance at far away distances, these parameters narrow up a bunch.

Jerry
 
At long range the barrel harmonics have a huge impact on group size. You can't see this at 100 and 200, so LR load development at short range is a waste of time and components.

I test at 500, to get the range of powder charges to test and then test at 900 or 1000. Preferably 1000.

My SD and ES tell me if I am making good ammo, but low numbers do not mean it is accurate.
 
Ganderite said:
At long range the barrel harmonics have a huge impact on group size. You can't see this at 100 and 200, so LR load development at short range is a waste of time and components.

I test at 500, to get the range of powder charges to test and then test at 900 or 1000. Preferably 1000.

My SD and ES tell me if I am making good ammo, but low numbers do not mean it is accurate.
Click to expand...

Ganderite,
Here’s how I see it (tell me if I am correct). Even with a good SD NUMBER, you can still have poor groups due to technique, components (scope, barrel, etc). But with poor SD NUMBERS, there is almost no chance you can get good results at longer distances.
 
I look at it this way. Ignore the effect of wind on group size.

The 0.5moa load groups great at short range, but due to the terrible ES/SD, the groups get larger the further out you go.
The average load groups averagely at short range, but due to the great ES/SD, the groups stay the same size out at longer ranges.

At some distance, the average load is now grouping better then the 0.5moa load.
 
Alpheus said:
I look at it this way. Ignore the effect of wind on group size.

The 0.5moa load groups great at short range, but due to the terrible ES/SD, the groups get larger the further out you go.
The average load groups averagely at short range, but due to the great ES/SD, the groups stay the same size out at longer ranges.

At some distance, the average load is now grouping better then the 0.5moa load.
Click to expand...

+1

That's what I think too
 
Alpheus said:
I look at it this way. Ignore the effect of wind on group size.

The 0.5moa load groups great at short range, but due to the terrible ES/SD, the groups get larger the further out you go.
The average load groups averagely at short range, but due to the great ES/SD, the groups stay the same size out at longer ranges.

At some distance, the average load is now grouping better then the 0.5moa load.
Click to expand...

Really easy to prove what matters ... just shoot on target at distances from 300yds and beyond... the further the better.

Paper doesn't lie and it will either prove the concept... or not. See if you can bring a few rifles out and see how the data applies over as many rifles are possible.

Find F class club matches and go shoot. Each shot is scored, plenty of time to record data and really easy to see what matters. Usually there are wind flags so you can reduce the confusion wind can add to your data.

If the club has E targets, you may even be able to download the impacts, scores and velocities.... Yes, most E targets will show downrange velocity which might be important if you really want to true your bullet BC.

Simple.

Jerry
 
laker415 said:
So I'm curious what you guys are more worried about when it comes to dialing in a load for distance shooting. I'm just starting to play around with neck tensions and also starting to shoot at longer distances. Currently I'm narrowing down a load for the 175 Sierra matchking in my 308.

I just shot 2 groups at 200 yards. One group was just over an inch for 5 shots with an SD of 10 and an ES of 27.

The other group was around 1.5" for 5 shots with an SD of 7 and an ES of 18.

What would you guys do? Perhaps I'm over thinking this. I have just been reading on how your ES becomes more of an issue at distance. Thoughts? Thanks
Click to expand...

SD/ES is important to target shooters, however accuracy/POI/small groups is the most important to me, as a hunter. I only measure my speed (for self interest) once my load development is complete. ES/SD is not that important for purpose of hunting.
 
A low SD is more important to raise the probability of a hit. ES relates more to group size. An ES < 10 ft/s is better for group size at distance.
I test at 300m for low ES and adjust powder charge to tune the barrel time. Typically the groups I get at 300m traslates by a factor of 4 at 1000yds.So a 2" group at 300 translates to an 8" at 1000
 
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