Bullet goes to sleep mode

[Bart B.]

What part of bullets' trajectory is perfectly horizontal and bullets' long axis also perfectly horizontal?

All targets perfectly vertical.

Please explain how bullets perfectly stabilized enter all targets 90 degrees from its surface.

No comment on bullet holes smaller in diameter than theirs is. 'Tis a well known fact they shrink from high pressure air all around them. That's why 22 caliber scoring plug gauges are used for 30 caliber bullets' holes.

 

[savagedasher]

The vertical on the target is the direction The bullet is moveing In relationship to the point of aim. With a tuner you can see that relationship change .
I don't understand why someone would tune a barrel perfect and put a tuner on.
All you could expect is the same . If the tuner is set correct .
Where Tuners work is with fixed ammo with the same Es Fixed doesn't mean just factory RF Hand loads with low Es is the same as fixed RF
With the use of a tuner It is no problem reducing the hole size in the paper at 100 yards . Not only bullet hole size but total bullet placement . Larry

 

[ASbobcat]

Yaw creates lift which is why it *does* change the path. That's how epicyclic swerve happens. It's just not as big as people seem to think.

Yes, but AGAIN, that effect is averaged out by spin. That's why rifling was invented. Less yaw means the radial deviation (group size) increases at reduced rate, but it will NEVER "shrink". Which I believe is the original point of the thread.

 

[Bart B.]

The vertical on the target is the direction The bullet is moveing In relationship to the point of aim. With a tuner you can see that relationship change .
I don't understand why someone would tune a barrel perfect and put a tuner on.
All you could expect is the same . If the tuner is set correct .
Where Tuners work is with fixed ammo with the same Es Fixed doesn't mean just factory RF Hand loads with low Es is the same as fixed RF
With the use of a tuner It is no problem reducing the hole size in the paper at 100 yards . Not only bullet hole size but total bullet placement .

Now you've lost me. Maybe someone can chime in and explain.

 

[dcali]

Yes, but AGAIN, that effect is averaged out by spin. That's why rifling was invented. Less yaw means the radial deviation (group size) increases at reduced rate, but it will NEVER "shrink". Which I believe is the original point of the thread.

I don't think we disagree on the bigger picture - but the swerving is larger near the muzzle. In that sense, the "go to sleep" crowd are correct. The trouble is we're talking thous, not inches, which makes the mythical shrinking groups still, well, mythical.

 

[Bart B.]

The trouble is we're talking thous, not inches, which makes the mythical shrinking groups still, well, mythical.

Except when slower bullets leave at a higher angle to the LOS than faster ones do. That's the barrel whip issue changing the muzzle axis angle.

 

[Richard Coody]

Except when slower bullets leave at a higher angle to the LOS than faster ones do. That's the barrel whip issue changing the muzzle axis angle.

That is why long range shooters strive for low ES. Shows up in the vertical. Much better technique then trying to tune a load for a specific range.

 

[Bart B.]

Except in some long range matches, you have to shoot the issued ammo and hope for the best.

Sometimes velocity numbers don't show up on target. I've shot through chronographs testing loads at 1000 yards to see what effects velocity has on vertical stringing. Some higher velocity bullets struck below call; some low velocity bullets went high. Only an inch or two, but still observed.

 

[Richard Coody]

Except in some long range matches, you have to shoot the issued ammo and hope for the best.

Sometimes velocity numbers don't show up on target. I've shot through chronographs testing loads at 1000 yards to see what effects velocity has on vertical stringing. Some higher velocity bullets struck below call; some low velocity bullets went high. Only an inch or two, but still observed.

So you are speaking of

Except in some long range matches, you have to shoot the issued ammo and hope for the best.

Sometimes velocity numbers don't show up on target. I've shot through chronographs testing loads at 1000 yards to see what effects velocity has on vertical stringing. Some higher velocity bullets struck below call; some low velocity bullets went high. Only an inch or two, but still observed.

So you are speaking of barrel harmonics not sleeping bullets.

Could be a load tuned like this might win Brian's contest.

 

[Bart B.]

Yes, barrel's bore axis at the muzzle vibrating in the vertical axis in the 3rd or 4th harmonic mode several hundred cycles per seconds above its resonant one at several dozen.

People have been tuning barrels moving weights nest their muzzles for rim and center fire match rifles fo short range use for several years. Brian Litz may want to ignore them.

I tried to contact Brian Litz via Berger's web site asking about positive compensation. No response. Wanted to know his thoughts about the Brit's documented stuff on positive compensation a century ago with 303 rifles shooting smaller groups at long range than mid range; shown in:

https://ia600701.us.archive.org/6/items/philtrans05900167/05900167.pdf

 

[dcali]

Bryan has commented on barrel vibrations many times. He's well aware of the phenomenon.

Yes, barrel's bore axis at the muzzle vibrating in the vertical axis in the 3rd or 4th harmonic mode several hundred cycles per seconds above its resonant one at several dozen.

People have been tuning barrels moving weights nest their muzzles for rim and center fire match rifles fo short range use for several years. Brian Litz may want to ignore them.

I tried to contact Brian Litz via Berger's web site asking about positive compensation. No response. Wanted to know his thoughts about the Brit's documented stuff on positive compensation a century ago with 303 rifles shooting smaller groups at long range than mid range; shown in:

https://ia600701.us.archive.org/6/items/philtrans05900167/05900167.pdf

That's a neat paper that I haven't seen before - what is it from? I did not notice any claims of smaller groups at longer ranges after a quick skim, however. What page are you referring to?

 

[Bart B.]

I did not notice any claims of smaller groups at longer ranges after a quick skim, however. What page are you referring to?

Page 329 showing the rifle barrel with 3 nodes (zero vibration) and the first one near the muzzle showing the muzzle axis angling up. Depending on the bullet's time to the muzzle, it'll leave at some point in that muzzle axis vertical swing.

 

[Richard Coody]

Page 329 showing the rifle barrel with 3 nodes (zero vibration) and the first one near the muzzle showing the muzzle axis angling up. Depending on the bullet's time to the muzzle, it'll leave at some point in that muzzle axis vertical swing.

Yep

That is what load development is all about

 

[Bart B.]

Agree. That often is reality.

Readers may want to check out posts 14 and 15 in:

http://forum.accurateshooter.com/threads/predicting-transonic-stability.3862971/#post-37008199

 

[dcali]

There's still nothing claiming that groups got smaller. I will accept positive compensation as a mechanism by which it is possible - in theory. In practice, it's not so simple.

The thing we're ignoring is that barrel vibration, while it has been demonstrated as a real effect (apparently as far back as 1901 - that's the earliest one I've ever seen) does not show that you can shoot smaller groups at longer ranges. It implies that it's possible if you have a zero dispersion rifle, but the numbers get difficult very quickly. By the time you layer on the bullet's inherent dispersion - which is theoretically (and in practice, I would say) linear with range, positive compensation is a small thing. It certainly doesn't account for tales of bullets shooting 3/4" at 100 yards and 1/2" at 200.

Incidentally, in that paper, the author rejects the idea of a recoiling barrel in favor of trying to tune the rifle to the ammunition. Harold Vaughn took the opposite approach in his book, and built a recoiling action. It worked. Very cool stuff.

 

[Bart B.]

By the time you layer on the bullet's inherent dispersion - which is theoretically (and in practice, I would say) linear with range, positive compensation is a small thing.

Bullets inherent dispersion in the vertical plane is not linear. They drop more in each ten yards of downrange horizontal travel at longer ranges than smaller ones. Any good ballistics software shows that happening as does sight settings for different ranges.

A 50 fps spread in muzzle velocity for 308 Win ammo causes about 1/10th MOA spread vertically (drop difference) at 100 yards'; at 1000 yards, it's a 2 MOA spread. Assuming all bullets leave at the exact same angle to the line of sight for every shot.

So do zeros; about 2 MOA up on sights for a 308 Win going from 200 to 300 yards, 7 MOA from 900 to 1000.

Their BC's change with velocity, too, so that also changes their trajectories in different range bands.

 

[dcali]

I don't mean ballistics. I mean the dispersion due to aerodynamic jump - from imbalance, tipping, etc. That initial jump is linear.

 

[Bart B.]

When the bullet leaves the muzzle they all jump off the bore axis the same amount from any unbalance?

 

[CharlieNC]

The OP started asking about why group sizes could decrease at range, and the title and much following discussion debated bullets going to sleep (jumping to a conclusion?). As many stated I think it is clear this can be explained by positive compensation. I believe VarmintAl shows clear examples of how this also varies based on the distance involved, ie tuning at the specific distance is required. Many will debate the validity of such computer simulation, but if we can put a man on the moon using similar methodology this is trivial by comparison. If memory serves I think Donovan has posted examples using targets at various distances, and shot simultaneously to demonstrate this. But I'm a senior citizen and memory isn't always my best trait.

 

[dcali]

When the bullet leaves the muzzle they all jump off the bore axis the same amount from any unbalance?

No, the more imbalance, the greater the angle of departure. But the dispersion due to that angle is linear with range.