MOA at one distance,but not others.

[RTK]

Please get the guy to post the millitary test report.

Bullets don't/can't travel in a 1/2 MOA elliptical path.

Bryan Litz proved that long ago.

-- richard

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.

 

[Bart B]

Read my post again about a guy that read some military test and it will answer that question. It is not the fact that it is changing path or moving closer, just not deviating anymore at distance..
Example,,,, IF a bullet travels in say, a 1 inch elliptical path at 100 yards, that's 1 MOA, but at 200 yards that 1 inch elliptical path is 1/2MOA and so on and so forth

I well understand the premis behind this concept. Dr. F. W. Mann experimented with unbalanced bullets in the early 1900's that proved this happens then documented it with pictures of targets placed every 10 yards or so up through 100 yards. Long, heavy lead bullets had a hole drilled in them to unbalance them and they were loaded with the hole indexed at the same point for each shot. Those targets proved the bullets traveled a cork screw path to the target.

If a bullet travels in a 1-inch cork screw or elliptical path at 100 yards and stays that way at longer ranges, how does it go from a zero MOA or zero inch path at the muzzle to that 1-inch diameter one at some distance before it gets to 100 yards then stay there such that the middle of that path has exactly the same trajectory regardless of what velocity it left the muzzle at? Do they all have the same drop down range for different muzzle velocities?

How does anyone (a benchrester who will set a 100 yard record?) orient such bullets in the chamber so they always start their cork screw path at the same distance and direction so they arrive at the 100 yard target such that they're all at the 3-o'clock position in their 1 inch diameter cork screw path and shoot a 1/16 inch group? If those bullets can't be "measured" to find out which part of them has to be placed at the same place in the chamber, they'll shoot a donut group an inch in diameter.

 

[rscott5028]

I well understand the premis behind this concept. Dr. F. W. Mann experimented with unbalanced bullets in the early 1900's that proved this happens then documented it with pictures of targets placed every 10 yards or so up through 100 yards. Long, heavy lead bullets had a hole drilled in them to unbalance them and they were loaded with the hole indexed at the same point for each shot. Those targets proved the bullets traveled a cork screw path to the target.

If a bullet travels in a 1-inch cork screw or elliptical path at 100 yards and stays that way at longer ranges, how does it go from a zero MOA or zero inch path at the muzzle to that 1-inch diameter one at some distance before it gets to 100 yards then stay there such that the middle of that path has exactly the same trajectory regardless of what velocity it left the muzzle at? Do they all have the same drop down range for different muzzle velocities?

How does anyone (a benchrester who will set a 100 yard record?) orient such bullets in the chamber so they always start their cork screw path at the same distance and direction so they arrive at the 100 yard target such that they're all at the 3-o'clock position in their 1 inch diameter cork screw path and shoot a 1/16 inch group? If those bullets can't be "measured" to find out which part of them has to be placed at the same place in the chamber, they'll shoot a donut group an inch in diameter.

Great info Bart.

And, a musket can shoot a tighter group than a modern benchrest rifle. But, it's not statistically very likely.

So, I'd like to know how this phenomenon could be possible in a consistent and repeatable way with a shoulder fired rifle using modern hunting or match grade bullets.

-- richard

 

[RTK]

If a bullet travels in a 1-inch cork screw or elliptical path at 100 yards and stays that way at longer ranges, how does it go from a zero MOA or zero inch path at the muzzle to that 1-inch diameter one at some distance before it gets to 100 yards then stay there such that the middle of that path has exactly the same trajectory regardless of what velocity it left the muzzle at? Do they all have the same drop down range for different muzzle velocities?

.

I really have no idea whether it really happens or not. I still can't see in my mind how you can tighten up a group at 300 vs 100, just repeating a "plausible" explanation. If it's crap at 100 I doubt it's gonna get better the further you shot, on the other hand if it is good at 100 it should tend to stay that way.

 

[Bart B]

I still can't see in my mind how you can tighten up a group at 300 vs 100, just repeating a "plausible" explanation. If it's crap at 100 I doubt it's gonna get better the further you shot, on the other hand if it is good at 100 it should tend to stay that way.

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. For more details, contact the Firearms guy in the UK NRA at [email protected] and ask him about it. He may give you some links to this interesting phenomenon. When the Brits started using the 7.62 NATO round and better extruded and ball powders, the SMLE's didn't fare as well. That's why in 1972, a British gunsmith (George Swenson) designed a single shot, 4-lug, front locking target rifle action (Swing action) and got the UK NRA to allow it to be used in mid and long range matches as it shot arsenal 7.62 NATO ammo better than the SMLE's shot arsenal .303 ammo. The whole British Commonwealth switched over to the Swing action except South Africa which had then started making the famous and very good single-shot Musgrave action (solid bottom, M98 Mauser style)

One of the US military rifle teams (Army or Marine Corps) reported years ago that accuracy tests with the M14NM's showed smaller MOA's at 600 yards than 300. Reason was/is the gas port about mid point in the barrel ejecting gas downwards pushed the barrel up at that point making the bore axis at the muzzle point down. Higher port pressure caused more down angle at the muzzle and 'cause bullets left faster with that higher pressure, they needed less elevation angle to strike center. The reverse happens with slower bullets and lower pressure; muzzle axis is higher when the bullet leave so its greater drop is compensated for.

 

[rscott5028]

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. For more details, contact the Firearms guy in the UK NRA at [email protected] and ask him about it. He may give you some links to this interesting phenomenon. When the Brits started using the 7.62 NATO round and better extruded and ball powders, the SMLE's didn't fare as well. That's why in 1972, a British gunsmith (George Swenson) designed a single shot, 4-lug, front locking target rifle action (Swing action) and got the UK NRA to allow it to be used in mid and long range matches as it shot arsenal 7.62 NATO ammo better than the SMLE's shot arsenal .303 ammo. The whole British Commonwealth switched over to the Swing action except South Africa which had then started making the famous and very good single-shot Musgrave action (solid bottom, M98 Mauser style)

One of the US military rifle teams (Army or Marine Corps) reported years ago that accuracy tests with the M14NM's showed smaller MOA's at 600 yards than 300. Reason was/is the gas port about mid point in the barrel ejecting gas downwards pushed the barrel up at that point making the bore axis at the muzzle point down. Higher port pressure caused more down angle at the muzzle and 'cause bullets left faster with that higher pressure, they needed less elevation angle to strike center. The reverse happens with slower bullets and lower pressure; muzzle axis is higher when the bullet leave so its greater drop is compensated for.

If this is the case, then it would only account for vertical dispersion.

Even at that, it seems unlikely (though possible) given that variable MV has a greater angular effect at increasing distances.

The table below shows how drop from bore line accelerates as time and distance increase.
e.g.

308 Win, FGMM 168 SMK
drop from
YDS bore line
--- ---------
FPS-->> 2650 2700
100 = -2.6 -2.5 .10MOA
300 = -25.9 -24.9 .33MOA
600 = -124.1 -119.2 .82MOA

...not saying it couldn't happen. Rather, it seems like a crap shoot if we're talking about shoulder fired weapons.

In fact, the above table probably better illustrates why people develop great loads at 100yds that don't do well at long range.

-- richard

 

[Bart B]

Regarding the SMLE's better accuracy at long range with arsenal's Cordite charged .303 ammo:

If this is the case, then it would only account for vertical dispersion.

Even at that, it seems unlikely (though possible) given that variable MV has a greater angular effect at increasing distances.

It's the vertical shot dispersion that was improved. It all happened during the muzzle axis up swing near its greatest amount. Bullets leaving at lower muzzle velocities exited at higher muzzle axis angles; faster ones at lower angles.

 

[Mikecr]

There are many theories as to if/why some rifles may consistently and repeatably improve their MOA accuracy at increasing distances.

But, I have yet to see a statistically valid, scientific experiement that proves that the phenomenon actually exits. ...much less, proof as to the why part

I also have never seen evidence, anecdotal or otherwise, that 'some rifles' shoot tighter moa with increasing distance. And this is not at all what I meant to imply.
I'm also sure elliptical swerve has been eliminated from the mystery.

What I meant to imply was that 'some shooters', 'with a certain combination of shooting system', do better at distance(in moa) than up close. That's me.
That don't mean I shoot tighter in moa out to just any ole distance though.
But 100yds-vs-500yds?
Given very good conditions, I could consistently shoot better at 500 than I could at 100.

I believe it will not be proven through peer review, because this represents a change of conditions(different shooter). If it's to be proven, it will have to be by someone causing it.
Which takes it back to the human brain.

Our brains paint pictures for us. They compile sensed information & fill in the blanks for us.
Wiht htis, j coyld missprll ervy wopd id thes setnence, andd uou sumhow unverstand jt anywey.

 

[rscott5028]

I also have never seen evidence, anecdotal or otherwise, that 'some rifles' shoot tighter moa with increasing distance. And this is not at all what I meant to imply.
I'm also sure elliptical swerve has been eliminated from the mystery.

What I meant to imply was that 'some shooters', 'with a certain combination of shooting system', do better at distance(in moa) than up close. That's me.
That don't mean I shoot tighter in moa out to just any ole distance though.
But 100yds-vs-500yds?
Given very good conditions, I could consistently shoot better at 500 than I could at 100.

I believe it will not be proven through peer review, because this represents a change of conditions(different shooter). If it's to be proven, it will have to be by someone causing it.
Which takes it back to the human brain.

Our brains paint pictures for us. They compile sensed information & fill in the blanks for us.
Wiht htis, j coyld missprll ervy wopd id thes setnence, andd uou sumhow unverstand jt anywey.

I'm totally on board with that explanation.

100yds gets pretty boring after a while.

-- richard

 

[1SevenZero]

Okay, so I busted out a book I bought about 7 years ago. Understanding Firearm Ballistics Basics to Advanced by Robert A. Rinker.

Chapter 5 (p. 60) - Compensation - "Some rifles are believed to shoot tighter groups in the vertical plane at the longer ranges than at the shorter ranges." "Favorable compensation is where lower muzzle velocity delivers shots at a slightly higherangle, consequently decreasing the element of the vertical spread at long range that results from velocity variations and producing a small spread."

He goes on to say on the same page.

"NOTE: From a practical point of view, it is illogical for a group to be tighter at a long range than at a shorter range. If so, it would be a freak occurrence and not likely to happen on a regular basis. Dispersion will always become greater in proportion to range. For the opposite to occur the projectiles would have to turn inward from whatever track they were following. If they were curving to the left, they would have to swing back to the right, and if they were on the right turning downward they would have to turn left and curve upwards."

Chapter 18 (p. 263) - Dispersion at Range - " It is an error to believe that group size will stay in proportion as the range increases. In other words if a rifle will shoot a 2" group at 200 yards it will not shoot a 4" group at 400 yards. When the distance is doubled the group size will almost always be more than double."

He continues on the same page.

"With the decreasing velocity and both the side deflection and drop increasing by accelerated motion, the group cannot change at a proportional rate."

He goes on to say the right equipment and right shooter can reduce this effect.

So....The last part totally gun)a hole in my theory that a gun capable of MOA accuracy at 100 should be capable of MOA at 1000. However it sounds like it is due to ballistics and not the rifle.

Also to me it reads that it is impossible for a rifle to shoot tigher groups at a mid to long range than up close, and if it does it would be a freak occurance and not a regular occurance.

It's a pretty good book...I should probably read it again.

 

[lsm62]

I also have never seen evidence, anecdotal or otherwise, that 'some rifles' shoot tighter moa with increasing distance. And this is not at all what I meant to imply.
I'm also sure elliptical swerve has been eliminated from the mystery.

What I meant to imply was that 'some shooters', 'with a certain combination of shooting system', do better at distance(in moa) than up close. That's me.
That don't mean I shoot tighter in moa out to just any ole distance though.
But 100yds-vs-500yds?
Given very good conditions, I could consistently shoot better at 500 than I could at 100.

I believe it will not be proven through peer review, because this represents a change of conditions(different shooter). If it's to be proven, it will have to be by someone causing it.
Which takes it back to the human brain.

Our brains paint pictures for us. They compile sensed information & fill in the blanks for us.
Wiht htis, j coyld missprll ervy wopd id thes setnence, andd uou sumhow unverstand jt anywey.

I love this book. Highly recomend it to anyone getting into shooting long range. I you could shoot a rifle in a vacuum then it would remain sub moa at any range but as stated prior the ballistics of the projectile are subject to many variables that will pull or push it off course and the further you shoot the more these variables affect the projectile. Hence causing group sizes to increase as the range increases.

 

[Mikecr]

Also to me it reads that it is impossible for a rifle to shoot tigher groups at a mid to long range than up close, and if it does it would be a freak occurance and not a regular occurance.

The topic here is MOA at distance, and not tighter grouping.
Also, Rinker was expressing practical terms. Grouping rather than accuracy, assumed velocity and air density spreads, common variances in components from shot to shot.

He provides basis for testing and tweaking loads at furthest distance used.
This typically opens near grouping while improving far grouping. I suppose it could be accepted as a freak occurence if near grouping opened so much as to exceed far grouping.
But this is w/regard to equipment(does not account for the shooter using it), and gross grouping measurements(rather than MOA).

He didn't dispell this subject. We know dispersion doesn't undo itself.

 

[1SevenZero]

The topic here is MOA at distance, and not tighter grouping. The topic is about grouping. I apologize if the thread title does not make this clear.
Also, Rinker was expressing practical terms.Grouping rather than accuracy, assumed velocity and air density spreads, common variances in components from shot to shot.

He provides basis for testing and tweaking loads at furthest distance used. In my opinion the book far exceeds the above statement, and delves into the science that surrounds ballistics.
This typically opens near grouping while improving far grouping. I suppose it could be accepted as a freak occurence if near grouping opened so much as to exceed far grouping. I would consider this a freak occurrence, and it appears as though Rinker would to. But this is w/regard to equipment(does not account for the shooter using it), and gross grouping measurements(rather than MOA).

He didn't dispell this subject. We know dispersion doesn't undo itself.

Could you please elaborate? This statement confuses me.

 

[Bart B]

Engineering calculations and measurements on positive compensation and bullets' exit at different muzzle angles; centerfire and rimfire rifles:

Barrel Tuner Analysis -- FEA Dynamic Analysis of Esten's Rifle with/without a Tuner.

Using barrel vibrations to tune a barrel