Group size evaluation

[Wyo_hntr]

But the whole point of this convo is that you can only zero your optic to within an inch and a half or whatever arbitrary number.

What is the cause of said dispersion?

Gee I don't know. What do you think is the most likely cause? (Hint: form already told you)

 

[JF_Idaho]

Gee I don't know. What do you think is the most likely cause? (Hint: form already told you)

No, he didn't. Just reread the posts.

All that's been discussed is what is. Never why is.

I really don't understand why the question of why, and what scientific and/or contollable/uncontrollable factors play into overall dispersion offend either of you.

 

[eoperator]

What is the cause of said dispersion?

Hornady podcast #57 dispersion would be a good place to start.

 

[WKR]

A “30 shot Extreme spread sub 2moa” guarantee”- means a whole hell of a lot more than a “.25 moa 3 shot, cold bore, match ammo” guarantee. The first is real and provable, the second is window dressing nononsense.

Within that statement lies the problem.
The common consumer will look at a verified sub 2 moa 30 shot ES and say that's a bad shooting rifle.

I see that we agree on that aspect, and I dont think there will ever be a change in the market to implement these ideas and solutions. As they say, ignorance is bliss, and it will continue down the path we are already on where the manufacturers and some custom rifle builders will continue to produce cherry picked 3 shot groups to sell their rifles.


To reply to your previous comment, where are you deriving the 95% probability from?

 

[hereinaz]

The average consumer is ignorant and wants simple. That’s why the guarantee is 3 shots. The industry won’t try to change the consumer. Look at what Hornady did and the podcast still doesn’t get to the average consumer.

Group size grows with more shots because there are multiple factors that move a bullet any one direction. So to get the furthest shot far left at 9:00, the trigger press has to push left, the recoil has to move left, the “barrel harmonics” has to push left, the bullet engraving needs to push it left, the bullet needs to enter the throat a little left, the bullet’s wobble need to be left, etc.

If you get half of the factors going right and half going left, they can offset.

That is why the cone grows. So many little minute factors that we can’t even measure or even know make up the factors for dispersion.

 

[cricket1974]

very intresting

 

[aschuler]

To reply to your previous comment, where are you deriving the 95% probability from?

I think 95% is generally used because dispersion follows a normal distribution. In that case 68% of your samples will fall within 1 standard deviation , and 95% of your samples will fall within 2 standard deviations. 95% is a convenient "close enough to perfect".

 

[Formidilosus]

Form,

Ok, well that was a lot of words just to throw out a couple insults.

Where did I insult you?

So 100fps ES doesn't increase dispersion? I'm guessing dispersion is caused by magic?

Right on. Got it.

Sometimes, often actually, loads with large velocity ES do shoot well.

 

[hereinaz]

Sometimes, often actually, loads with large velocity ES do shoot well.

The caveat is that ES variation creates larger vertical dispersion as the distance increases.

 

[Formidilosus]

The caveat is that ES variation creates larger vertical dispersion as the distance increases.

Not always. You cannot use ES as a surrogate for precision. Precision is the determiner of precision. Lots of bad MV ES loads shoot well at distance.

 

[JF_Idaho]

Where did I insult you?




Sometimes, often actually, loads with large velocity ES do shoot well.

Saying I'm not thinking critically, and that I don't even have a basic understanding aren't underhanded digs?

Just listened to the podcast he linked above. Hornady #57. 2 guys talking about science, not "magic", that affect dispersion.

Center of Gravity offset and the things that can enhance the effects of the offset, such as copper or even carbon fouling, which is obviously an ever changing variable, if not controlled.

And the statistical probability not being a quantifiable number because of the infinite number of variables make that impossible to determine.

If you have 2 similar quality barrels that can shoot a .5 moa group (3 shots), that doesn't mean they will both be "x moa" after 30 shots, if all else isn't equal. A heavier contour barrel will be less dispersion that the light contour barrel.

I understand your point that there are diminishing returns on chasing these minute details. Especially in a hunting scenario. And that is fair. But, I don't understand why it bothers people if someone does want to care and talk about something new, or more expansive than the same old stuff that gets talked about in multiple threads per day (i.e. drop-tests, and standard group sizes).

I love shooting and I do. But, it doesn't stop me from spending time thinking about what I can do better, and how the variables I can control be better. And an understanding of the variables I can't control, and what I can do to minimize them.

 

[WKR]

Lots of bad MV ES loads shoot well at distance.

Whilst this is true, and we can use factory loads as an example of good precision even when it has high velocity ES,

If you take two identical hand loads, but one is 100 fps slower/faster. Those two rounds will not have the same point of impact, within the given loads average, at 1000 yards.

 

[hereinaz]

Not always. You cannot use ES as a surrogate for precision. Precision is the determiner of precision. Lots of bad MV ES loads shoot well at distance.

I didn’t use ES as a surrogate for anything. I said it increases vertical dispersion, which it does.

Of course, it matters nothing at 100 yards, nothing at 200, nothing at 300, nothing at 400, and maybe start to see some at 500. But that is because the hunting target is relatively larger in relation to the dispersion and the time of flight is shorter and velocity degrades less.

So the questions are:

What do you mean “shoot well”?
What are you calling “at distance”?

 

[hereinaz]

I love shooting and I do. But, it doesn't stop me from spending time thinking about what I can do better, and how the variables I can control be better. And an understanding of the variables I can't control, and what I can do to minimize them.

Me too.

 

[Formidilosus]

Saying I'm not thinking critically, and that I don't even have a basic understanding aren't underhanded digs?

I don’t know you- why I would insult you. This isn’t twitter or Facebook and I don’t care about silliness.

Instead of reading it as a personal statement, reread it as a thought experiment.

Just listened to the podcast he linked above. Hornady #57. 2 guys talking about science, not "magic", that affect dispersion.

If you were asking what are the factors that cause dispersion- I didn’t read it that way, or understand that was your question. What you wrote read as if you believed there are too many variables to shoot a 30 shot group and get anything out of it because the gun is changing during those 30 shots.


If you want to know what individual causes of dispersion are, Brian Litz books from Applied Ballistics are the place to start.

If you have 2 similar quality barrels that can shoot a .5 moa group (3 shots), that doesn't mean they will both be "x moa" after 30 shots, if all else isn't equal.

Who said it did?

A heavier contour barrel will be less dispersion that the light contour barrel.

Maybe. Who’s tested that in a rigorous manner, and what were the differences?

I understand your point that there are diminishing returns on chasing these minute details. Especially in a hunting scenario. And that is fair. But, I don't understand why it bothers people if someone does want to care and talk about something new, or more expansive than the same old stuff that gets talked about in multiple threads per day (i.e. drop-tests, and standard group sizes).

Who’s bothered by talking about things? The issue, is when someone is worrying about the differences in metallurgy or the changes that happen in bore condition between shot 3 and shot 10… yet they can’t hit a 2 MOA target on demand.

love shooting and I do. But, it doesn't stop me from spending time thinking about what I can do better, and how the variables I can control be better. And an understanding of the variables I can't control, and what I can do to minimize them.

Sure. It also doesn’t mean that if you are asking questions that are minutia, yet it seems you don’t understand what the 99.5% cause of errors are, that someone won’t point it out. Worrying about something that causes 1% of your error, but ignoring what causes 70% is just mental masterbation. Unfortunately that is what the vast majority the shooting and hunting world do and push.
That is why there is a tendency here at times to focus on statically valid shot group sizes, scopes and rifles that are reliable, and shooting performance on demand from field positions- because if that isn’t locked on tight- none of the other nonsense matters.

 

[Formidilosus]

Whilst this is true, and we can use factory loads as an example of good precision even when it has high velocity ES,

If you take two identical hand loads, but one is 100 fps slower/faster. Those two rounds will not have the same point of impact, within the given loads average, at 1000 yards.

Not necessarily. The barrel is oscillating when the bullet exits. I have seen quite a few 60-80fps ES in MV combinations that shot sub 8” vertical at 800 yards for 20 shot groups. I had a 5.56mm gas gun that was over 100fps ES yet 600 yard 10 round groups were about 1.3 MOA.

MV ES matters so little in determining group size and hit rates on game animals at terminal ranges of projectiles for hunting, that I don’t use a chrono 99% of the time.

 

[Formidilosus]

I didn’t use ES as a surrogate for anything. I said it increases vertical dispersion, which it does.

No, it doesn’t always. Read the last post above this one. You can not just look at a calculator and say “well 20fps more MV results in a 3” higher impact at 900 yards, so ES causes vertical issues”.

Of course, it matters nothing at 100 yards, nothing at 200, nothing at 300, nothing at 400, and maybe start to see some at 500. But that is because the hunting target is relatively larger in relation to the dispersion and the time of flight is shorter and velocity degrades less.

Again, that’s theory- not reality. If you don’t check a load at distance (again using statistically valid shot group sizes) you don’t know whether it will or won’t shoot at distance based on MV ES.
As an example, I believe Blaine at UM has won multiple 1,000y BR matches with a load that has a crazy bad MV ES, yet shoot groups incredibly well at 1,000 yards.

So the questions are:

What do you mean “shoot well”?

Depends on context. For hunting on animals, 1.5’ish MOA or less. For field competitions- 1.1-1.2 MOA or less.

What are you calling “at distance”?

Terminal range of projectiles for hunting in this context, so 800 to 900 yards.

 

[hereinaz]

Not necessarily. The barrel is oscillating when the bullet exits. I have seen quite a few 60-80fps ES in MV combinations that shot sub 8” vertical at 800 yards for 20 shot groups. I had a 5.56mm gas gun that was over 100fps ES yet 600 yard 10 round groups were about 1.3 MOA.

MV ES matters so little in determining group size and hit rates on game animals at terminal ranges of projectiles for hunting, that I don’t use a chrono 99% of the time

Has the barrel oscillation theory to cancel out MV been tested?

What was the cartridge?
What size dispersion die the load shoot at 100 yards?

Agree that it doesn’t matter for most hunting situations.

 

[Formidilosus]

Has the barrel oscillation theory to cancel out MV been tested?

What was the cartridge?
What size dispersion die the load shoot at 100 yards?

Agree that it doesn’t matter for most hunting situations.

Specifically as it pertains to “positive compensation” theory? I have read a few, though the ones I remember recently weren’t about shoulder fired small arms.
As to whether bullets exit the muzzle at different points in the muzzle oscillation vertical plane- absolutely. Thats all cartridges.


What you wrote is that higher ES in MV means larger shot group/vertical spread at distance- correct?
That is not factually true every time. In reality relatively large MV ES’s can result in very good shooting combinations at even long hunting ranges, and just as many great low MV ES loads shoot like crap. You simply cannot know what how a load will shoot until you shoot it.

To that point, I have yet to see a rifle/load combo that shot significantly worse at distance than it does at 100-300 yards. 30 shot groups of 1.2’ish MOA at 100 yards, have been 30 shot groups of 1.2’ish MOA at 300 yards, which have been 1.2’ish MOA groups at 600+ yards.

 

[hereinaz]

Applied Ballistics article with a graph showing ES, more specifically SD matters. I am skeptical of the barrel harmonics theory as the reason it can be cancelled out at long range, but do acknowledge it has been reported to happen. It’s an anomaly whatever the cause.

The flip side is there should be barrels out there that are stringing shots based on harmonics if the MV is very consistent.

In the end, only the scoreboard matters. Can it kill. But, if you have high ES/SD expect to see it at 800-900—if you can shoot well enough to discern it.

https://appliedballisticsllc.com/wp-content/uploads/2020/08/BC_SD_Effects.pdf