ES/SD with larger sample size

[LR5Ranger]

I recently got a Garmin Xero, sure beats shooting “over the chrono”. In the past I would shoot a few rounds to get my general velocity and then get my dope through shooting on steel at range. But with the Garmin it’s too easy to set it up on the mat and get every shot I shoot the entire range session.

As a result, I’m seeing larger ES/SD numbers than I’m used to. I know that’s going to be the case with a larger sample size, but I haven’t seen a discussion on what normal numbers are in say a string of 20-30 rounds as opposed to a 5 shot string.

Last time I was out I had 10 rounds that had a SD of 11, but one low and one high that opened up the ES to 42 despite annealing, hand trickling loads to the kernel of powder etc. Is this normal? In the past I might have written it off to muzzle blast messing with the optical chrono but I’m not thinking the radar is wrong.

Thoughts?

 

[Dos XX]

What cartridge?

 

[LR5Ranger]

What cartridge?

In this case 7PRC. I just got the chrono a week ago and haven’t had the opportunity to try my pet loads for my other rifles. 175SMK and 45gr of Varget has always been an absolute winner for me in the 308, next time I go out I’m interested to see what the number are for it. Done a lot of shooting out to about 950 yards with that load.

 

[Dos XX]

In this case 7PRC. I just got the chrono a week ago and haven’t had the opportunity to try my pet loads for my other rifles. 175SMK and 45gr of Varget has always been an absolute winner for me in the 308, next time I go out I’m interested to see what the number are for it. Done a lot of shooting out to about 950 yards with that load.

Interesting. I thought it might have been a .223, which is a hard cartridge to get very small es/sd in.

.308 and Varget is like the easy button. I shot a lot of Power Pro 2000 in .308 at a time when Varget was in very short supply. It would not hold low es. It was a dense powder. You could shake a round and hear the powder. You could achieve very high velocities with it, but it was erratic.

 

[LR5Ranger]

Interesting. I thought it might have been a .223, which is a hard cartridge to get very small es/sd in.

Using virgin brass, I’m thinking maybe the outliers will come down once it’s Fire formed.

 

[Dos XX]

Using virgin brass, I’m thinking maybe the outliers will come down once it’s Fire formed.

Just curious, what length barrel?

 

[LR5Ranger]

Just curious, what length barrel?

22in. I might try a faster powder, I’m wondering if it might not be 100% burned by the time the bullet clears the barrel.

 

[Dos XX]

22in. I might try a faster powder, I’m wondering if it might not be 100% burned by the time the bullet clears the barrel.

That is what I was going to say. I have a 20" .260 and it will get to the point where it won't burn any more H4350, but you can still add it to the case.

 

[huntnful]

40 ES over 20 shots is pretty good from my larger sample testing.

 

[LR5Ranger]

40 ES over 20 shots is pretty good from my larger sample testing.

That’s reassuring. I’ve been having a heck of a time getting a new rifle to shoot and I’ve been just racking my brain for why. I’m pretty precise reloading but some guys claim single digits. I don’t sort by ogive or H2O capacity though.

 

[huntnful]

That’s reassuring. I’ve been having a heck of a time getting a new rifle to shoot and I’ve been just racking my brain for why. I’m pretty precise reloading but some guys claim single digits. I don’t sort by ogive or H2O capacity though.

I shoot single digit ES all the time with 3 shots too lol. But they're likely just nitpicking samples IMO.

Are you having a hard to actually getting it to physically shoot groups? Or are you just referring to the ES?

Some cartridges with bullet/powder combos absolutely shoot in 20 ES for large samples. But in general, I think 40 ES is realistic.

 

[LR5Ranger]

I shoot single digit ES all the time with 3 shots too lol. But they're likely just nitpicking samples IMO.

Are you having a hard to actually getting it to physically shoot groups? Or are you just referring to the ES?

Some cartridges with bullet/powder combos absolutely shoot in 20 ES for large samples. But in general, I think 40 ES is realistic.

I’m having a hard time getting it to shoot anything less than 1.7 MOA or so. I’ve changed powders, primers, bullets, neck tension, annealed cases, switched out muzzle devices, etc. My loaded rounds have a runout of about .001. I’m at a complete loss. Thus me worrying about an ES in the 40’s and a SD of 11.

 

[Dos XX]

Scope? Scope base? Barrel free floated? Bedding? Action screws?

You probably did all of that already.

 

[LR5Ranger]

Scope? Scope base? Barrel free floated? Bedding? Action screws?

You probably did all of that already.

Yeah, everything torqued to spec with a gunsmiths torque wrench, barrel free floating and not touching the stock or scope, etc.

 

[huntnful]

What's the build and the barrel?

If you're using good components, a good scope/rings, and you tried that much, I would just junk the barrel. Is the action bedded?

 

[Jebel]

SD of 11 and ES in the 40s is good, measured over 20+ rounds. Use a ballistic calculator to see the MOA impact of a 40 fps difference on target. No, it’s not comparable to what you hear people report for 3-5 shot groups, but it’s better quality data so don’t worry about it.

 

[LR5Ranger]

What's the build and the barrel?

If you're using good components, a good scope/rings, and you tried that much, I would just junk the barrel. Is the action bedded?

It’s a new rifle from a well known manufacturer. Sounds like they are going to take it back and go through it to see if they can find anything wrong with it. I don’t want to drop the name since they are going to make it right. Before I go to all the trouble to send it back I’ve been racking my brain on what could be wrong with the thing; is it just something I’m doing?

So that’s how I got to be pondering ES/SD numbers tonight.

 

[Koda_]

I’m having a hard time getting it to shoot anything less than 1.7 MOA or so. I’ve changed powders, primers, bullets, neck tension, annealed cases, switched out muzzle devices, etc. My loaded rounds have a runout of about .001. I’m at a complete loss. Thus me worrying about an ES in the 40’s and a SD of 11.

Adjust your seating depth in .003" increments to shrink your group size. .003" may seem small but you want to pick the depth in the middle of the precision node of at least 3 samples.

A larger sample size will increase ES, dont beat yourself up over it. Im not certain what the max should be as a general rule but Ive read 50ES max is "good ammo", 35 max is "really good". My guess is whats acceptable has more to do with how far you wish to shoot with the ammo... a good article explaining this:

Long Range Shooting: Understanding Extreme Spread And Standard Deviation - Guns and Ammo

With the increase in interest in long-range shooting, the terms extreme spread (ES) and standard deviation (SD) are being thrown around a lot.

www.gunsandammo.com

 

[huntnful]

It’s a new rifle from a well known manufacturer. Sounds like they are going to take it back and go through it to see if they can find anything wrong with it. I don’t want to drop the name since they are going to make it right. Before I go to all the trouble to send it back I’ve been racking my brain on what could be wrong with the thing; is it just something I’m doing?

So that’s how I got to be pondering ES/SD numbers tonight.

Understandable for sure. Reason I ask is some platforms just aren't worth putting a new barrel on out of your own pocket. Action quality, stock quality, bedding quality can all just stack accuracy against you, and a barrel won't make up for all of it.

If they're going to make it right, that's awesome though.

If you can't load a quality round, with a known bullet and powder and have it not shoot under 1 MOA most of the time right out of the gate, you're in for some headaches if accuracy is top priority IME.

 

[LR5Ranger]

Understandable for sure. Reason I ask is some platforms just aren't worth putting a new barrel on out of your own pocket. Action quality, stock quality, bedding quality can all just stack accuracy against you, and a barrel won't make up for all of it.

If they're going to make it right, that's awesome though.

If you can't load a quality round, with a known bullet and powder and have it not shoot under 1 MOA most of the time right out of the gate, you're in for some headaches if accuracy is top priority IME.

Yeah this seems to be an anomaly.