MOA at one distance,but not others.

[Mikecr]

I hear people talk about their rifles shooting MOA, or sub up to certain distances, but then shooting worse than MOA after exceeding that distance. Is that possible?

To me it seems if a rifle is mechanically MOA capable at one distance than it would be capable at all distances.

I would think this would be the result of shooter error, or poor performing loads.

Your thread starting statements indicate MOA of shooting at various distances.

The topic is about grouping.

Now you're completely changing the subject. Don't do that 7 pages into YOUR thread.

MOA of accuracy is not the same as grouping. MOA of grouping is not the same as grouping otherwise.
A 1" group at 100yds is smaller than a 2.5" group at 500yds. One of these groups can be described as .955MOA of grouping, and the other .477MOA of grouping.
Accuracy-wise, both could be any value of MOA to center of mark, and that 1" group could be .477MOA of accuracy.

Was there some portion of Rinker's writing that actually held to standards in MOA of SHOOTING? What you quoted doesn't, and departs from the context of this thread.
It is very possible, I assure you, to shoot 2" groups at 200yds, followed by 4" groups, or 2"groups, at 400yds.
Rinker is saying that 2" of physical dispersion will result in AT LEAST 4" of dispersion by 400yds.
And I think pretty much everyone knows this today.

But when someone who can SHOOT 1/2MOA at 400yds, can do no better than 3/4MOA at 200yds, some of that 3/4MOA is NOT physical(ballistic) dispersion. Some of it, somehow, is caused by the shooter. That is the mystery in discussion so far.
It's what you started and should stick to.

 

[Bart B]

Your thread starting statements indicate MOA of shooting at various distances.

Now you're completely changing the subject. Don't do that 7 pages into YOUR thread.

MOA of accuracy is not the same as grouping. MOA of grouping is not the same as grouping otherwise.

Rinker is saying that 2" of physical dispersion will result in AT LEAST 4" of dispersion by 400yds.
And I think pretty much everyone knows this today.

Mike, thanks for bringing this to the attention of parties concerned. I, too, was concerned about changing horses in the middle of the stream. You covered it well.

But when someone who can SHOOT 1/2MOA at 400yds, can do no better than 3/4MOA at 200yds, some of that 3/4MOA is NOT physical(ballistic) dispersion. Some of it, somehow, is caused by the shooter. That is the mystery in discussion so far.
It's what you started and should stick to.

Some vertical dispersion way down range may well be caused by the shooter. But there's enough proof in the experiments I linked to to show it's plausible to be caused by natural barrel whip in the vertical axis when bullets leave at different points in the muzzle axes up swing due to their velocity spread.

I've been given the address of the UK's NRA Museum's Curator at Bisley, England. He is a world authority on .303 SMLE ammunition in addition to being an international shot and he's represented Great Britian at Palma matches. He doesn't have e-mail contact, so I'll have to write him a letter asking for amplification of the positive compensation phenomena of SMLE's.

 

[1SevenZero]

Your thread starting statements indicate MOA of shooting at various distances.

Now you're completely changing the subject. Don't do that 7 pages into YOUR thread. I don't feel as though I am as MOA is commonly used to describe a rifles grouping size.

MOA of accuracy is not the same as grouping. MOA of grouping is not the same as grouping otherwise.
A 1" group at 100yds is smaller than a 2.5" group at 500yds. One of these groups can be described as .955MOA of grouping, and the other .477MOA of grouping.
Accuracy-wise, both could be any value of MOA to center of mark, and that 1" group could be .477MOA of accuracy.

Was there some portion of Rinker's writing that actually held to standards in MOA of SHOOTING? It doesn't have to be for it to still apply. What you quoted doesn't, and departs from the context of this thread. I don't feel at all that what I posted departs from the context of his thread. Why do you feel as though it does?
It is very possible, I assure you, to shoot 2" groups at 200yds, followed by 4" groups, or 2"groups, at 400yds.
Rinker is saying that 2" of physical dispersion will result in AT LEAST 4" of dispersion by 400yds.
And I think pretty much everyone knows this today.

But when someone who can SHOOT 1/2MOA at 400yds, can do no better than 3/4MOA at 200yds, some of that 3/4MOA is NOT physical(ballistic) dispersion. Some of it, somehow, is caused by the shooter. That is the mystery in discussion so far.
It's what you started and should stick to. I believe I have.

If you guys feel as though what I'm saying is not inline with the course the thread has taken then don't humor it and continue on with your discussion.

 

[Mikecr]

it's plausible to be caused by natural barrel whip in the vertical axis when bullets leave at different points in the muzzle axes up swing due to their velocity spread.

This is true, and is another factor beyond ballistic math.

It's why load developing at a specific distance can possibly improve grouping there -while at the same time degrading performance at other distances(including closer). It doesn't contribute to every form of 'shrinking moa of shooting', but could be taken as such, and proven.
Only problem is proving it with a shooting system/load that actually does it, and under the causal conditions observed.

A certain barrel & certain load & certain ES limit(barrel timing window) could present reduced vertical at say 600yds, while vertical at 450yds and 750yds might be worse than predicted.
IMO, it's a ballistic anomaly that any distant shooting competitor would hope to find.
To find the 'hummer' that is

 

[Bart B]

A certain barrel & certain load & certain ES limit(barrel timing window) could present reduced vertical at say 600yds, while vertical at 450yds and 750yds might be worse than predicted.

Exactly.

I seem to remember one of the older South African fullbore shooters mentioning that the .303 SMLE's seemed to have their "crossover" point where slower bullets' higher trajectory arc cross the lower one of faster bullet somewhere around 700 to 800 yards. At 1000 yards, slower bullets strike lower than the faster ones, but at 400 yards, the slower ones struck higher than the faster ones.

 

[rscott5028]

Even with all the discussion about cases where the angle of departure might be optmized for some given distance (thereby sub-optimal at another), one still has to consider the horizontal component of groups.

I suppose the significance might be somewhat dependent on the context, hunting/cold bore, standing, prone, benchrest aggregates, clay/egg shoots, f-class long shot srings... smallest 3 shot group ever, extreme spread, POA=POI.

Unless you're restricted to factory ammo, velocity spread can be managed. External forces come to bear, and marksmanship takes over.

-- richard

 

[justgoto]

Don't know who is right or wrong, but this gentleman said the military via slow motion photography said they do..................I would imagine a de-stabilized bullet can do a 1/2 moa eiliptical type path

If they don't as you say, then I can't see how anything to do with the bullet can make them "sleep" or "stabilize" with distance.

I know of a few.
[ame=http://www.youtube.com/watch?v=Z7FMki6dlKg]shot out tank shell slow motion - YouTube[/ame]
and
[ame=http://www.youtube.com/watch?v=Num9TR7wlrw]Ballistic Shell Fired In Slow Motion - YouTube[/ame]

 

[Bart B]

Check out the following web site with selected parts of Dr. Mann's book from 1909.

The bullet's flight from powder to target: the internal and external ... - Google Books

Click on the site's links to the following:

* Gyration and Oscillation, page 221

* Cause of y Illustrated, page 276, then scroll down to Plate 27 on page 281.

The other links to sections of the book area lso interesting.

 

[rscott5028]

Check out the following web site with selected parts of Dr. Mann's book from 1909.

The bullet's flight from powder to target: the internal and external ... - Google Books

Click on the site's links to the following:

* Gyration and Oscillation, page 221

* Cause of y Illustrated, page 276, then scroll down to Plate 27 on page 281.

The other links to sections of the book area lso interesting.

That's great reading, but has been superceded by many works including Litz' modelling that showed that the absolute worst case for pitch and yaw when modelling epicyclic swerve of a bullet in flight would never excede one half caliber.

In all cases, the bullet as a whole continued to depart from its original path rather than "correct" itself.

I'm no doubt not paraphrasing him well. So, read his books and/or ask Bryan.

-- richard

 

[Bart B]

That's great reading, but has been superceded by many works including Litz' modelling that showed that the absolute worst case for pitch and yaw when modelling epicyclic swerve of a bullet in flight would never excede one half caliber.

Really not surprising 'cause bullets made these days are much better balanced than a hundred years ago. And Dr. Mann intentionally unbalanced bullets to better show their cork screw shaped paths.

It wasn't until the late 1920's that arsenals making the then new 172-gr. FMJBT machine gun bullet that both short and long range accuracy with a given bullet was greatly improved. WRA/WCC's FMJBT 180-gr. match bullets used in commercial .30-06 match ammo was the next step in reducing that epicyclic swerve of a bullet in flight.

 

[Michael Eichele]

Forget it. I will just get crucified.

****Deleted******

 

[Bart B]

Deleted

 

[Mikecr]

Couple questions michael;
How does the 178AMAX load shoot at ~600yds?
Is it supersonic through 1kyds?

 

[Bart B]

Well, the Brit's SMLE did shoot arsenal .303 ammo (Cordite propellant; huge muzzle velocity spreads) better at longer ranges; that's what I've said before.

Found what I was looking for. Was in contact with the UK Palma Team's Captain and he sent me email that triggered what I should look for. Here it is.

Skip the high level math formulas and look at the last page. That's the best part showing what happens; first with the Lee-Metford and it repeated in the SMLE.

Vibrations of Rifle Barrels : Mallock, A. : Free Download & Streaming : Internet Archive

On the left side, click on PDF in the "View the book" window.