22 LR Ballistics and Plotting Sheet for PRS CRPS Style shooting

[Maple57]

22 LR Ballistics and Plotting Sheet for PRS CRPS Style shooting.

Over the thanksgiving weekend I had a little time and noodled around in MS Paint to create this.

This was developed for 71 degrees F, but next time I have a little time, I'll add a second line for each distance to show the relative effect of colder weather.

I'll be testing this format out as a means of tracking try dope vs actual during PRS matches. This way there's a history that can be studied to identify where improvement can be made.

The resolution on this image is reduced to fit, so it wont read as well as the full size version.

This was made for MOA, since that's what I use. Sorry Mil guys.

 

[adamg]

I am highly dubious that aerodynamic jump manifests itself as the vertical shift that our calculators and the formulas that they use claim.

It should be one of the easier things to test, unfortunately testing it is not possible on a square approved range which is where I do all my practice.

I set my Strelok Pro configuration to use the alternate formula, where it computed as a percentage of wind drift angular amount.

 

[Maple57]

I am highly dubious that aerodynamic jump manifests itself as the vertical shift that our calculators and the formulas that they use claim.

It should be one of the easier things to test, unfortunately testing it is not possible on a square approved range which is where I do all my practice.

I set my Strelok Pro configuration to use the alternate formula, where it computed as a percentage of wind drift angular amount.

Well, I cannot say with certainty how a 22 LR responds to aerodynamic jump, but I can assure you in F Class it occurs most absolutely. I can't image why a 22 LR would be any different.

 

[Walterfisher]

Well, I cannot say with certainty how a 22 LR responds to aerodynamic jump, but I can assure you in F Class it occurs most absolutely. I can't image why a 22 LR would be any different.

It's not. 22 LR ammo is so inconsistent and the dispersion at distance is so large that there is no accurate method of determining the aerodynamic jump. It is there but it is masked by the deficiencies of 22 LR ammo.

 

[Maple57]

It's not. 22 LR ammo is so inconsistent and the dispersion at distance is so large that there is no accurate method of determining the aerodynamic jump. It is there but it is masked by the deficiencies of 22 LR ammo.

Not true. If the effect occurs, and almost certainly does, it will apply to all fliers equally. You may not notice the effect on a single shot, but the over all group would move vertically with wind changes.

In this case, my money is on Bryan Litz.

 

[grauhanen]

Aerodynamic jump occurs with .22LR and its effects can be seen as near as 50 meters. To illustrate, a wind from 9 o'clock causes the round to strike a bit lower (and to the right). A 3 o'clock wind will push the bullet a wee bit higher (and to the left).

This is shown on most wind charts used for .22LR as seen below.

Confirmation of aerodynamic jump and .22LR was made by Robert McCoy in his 1990 study "Aerodynamic Characteristics of Caliber .22 Long Rifle Match Ammunition". In his conclusions on page 12, he notes in point 6

The effect of wind on the trajectory of caliber .22 match ammunition at 50 metres
range is to cause bullet impacts distributed along a 9:30/3:30 slant line. The left/right
deflection is accurately predicted by the classical wind drift formula, and the vertical
deflection is accurately predicted by the ballistic formula for aerodynamic jump. The
rifleman needs to make one click adjustment in elevation for every four clicks made
on windage.

See the McCoy pdf here https://apps.dtic.mil/dtic/tr/fulltext/u2/a229713.pdf

For a hit and miss discussion of aerodynamic jump and .22LR, see this thread, which includes a video based on evidence that's inconclusive https://www.snipershide.com/shooting/threads/aerodynamic-jump-with-22lr.6995652/

For a good discussion of wind charts, see https://www.rimfireaccuracy.com/Forum/index.php?threads/a-wind-chart.28674/

 

[Maple57]

The effect of wind on the trajectory of caliber .22 match ammunition at 50 metres
range is to cause bullet impacts distributed along a 9:30/3:30 slant line. The left/right
deflection is accurately predicted by the classical wind drift formula, and the vertical
deflection is accurately predicted by the ballistic formula for aerodynamic jump. The
rifleman needs to make one click adjustment in elevation for every four clicks made
on windage.

Keep in mind this is for 50 yards/meters. The 1:4 ratio would not apply as the distance is increased.

 

[adamg]

It's not. 22 LR ammo is so inconsistent and the dispersion at distance is so large that there is no accurate method of determining the aerodynamic jump. It is there but it is masked by the deficiencies of 22 LR ammo.

I agree that at 300+ m distance, you can't detect a 0.2mrad AJ effect.

At 25m, that same 0.2 mrad up when shooting with a 9:00 wind and a 0.2mrad down when shooting with a 3:00 wind is entirely measurable. And herein lies my problem with the formula - it does not factor in the time of flight / distance of flight. It would be the only external ballistic effect known to man that does not factor in these parameters.

 

[Maple57]

I agree that at 300+ m distance, you can't detect a 0.2mrad AJ effect.

At 25m, that same 0.2 mrad up when shooting with a 9:00 wind and a 0.2mrad down when shooting with a 3:00 wind is entirely measurable. And herein lies my problem with the formula - it does not factor in the time of flight / distance of flight. It would be the only external ballistic effect known to man that does not factor in these parameters.

Notice the slope of aerodynamic jump appears flatter at long range compared to short range. The relative flatness of AJ at longer distances would be the reason you don't think you notice it. It's there, but lost in what you perceive as noise.

Easy enough to prove to yourself if you can find a place where you can shoot in a 3 o'clock and 9 o'clock wind with targets at the same distance 180 degrees apart from the firing position. If there is an elevation difference, you'll know why.

 

[grauhanen]

Keep in mind this is for 50 yards/meters. The 1:4 ratio would not apply as the distance is increased.

Yes, you read correctly that McCoy says it's for 50 yards/meters. That's the distance at which the aperture adjustments he refers to are relevant.

As distance increases, there are many variables that will affect POI more and more. It's challenging enough to explain the causes at 50 and doing so at 100 even harder still. At further distances, it can become a real head scratcher, with or without ballistics programs or charts.

 

[Longstud]

Aerodynamic jump occurs with .22LR and its effects can be seen as near as 50 meters. To illustrate, a wind from 9 o'clock causes the round to strike a bit lower (and to the right). A 3 o'clock wind will push the bullet a wee bit higher (and to the left).

This is shown on most wind charts used for .22LR as seen below.

Confirmation of aerodynamic jump and .22LR was made by Robert McCoy in his 1990 study "Aerodynamic Characteristics of Caliber .22 Long Rifle Match Ammunition". In his conclusions on page 12, he notes in point 6

The effect of wind on the trajectory of caliber .22 match ammunition at 50 metres
range is to cause bullet impacts distributed along a 9:30/3:30 slant line. The left/right
deflection is accurately predicted by the classical wind drift formula, and the vertical
deflection is accurately predicted by the ballistic formula for aerodynamic jump. The
rifleman needs to make one click adjustment in elevation for every four clicks made
on windage.

See the McCoy pdf here https://apps.dtic.mil/dtic/tr/fulltext/u2/a229713.pdf

For a hit and miss discussion of aerodynamic jump and .22LR, see this thread, which includes a video based on evidence that's inconclusive https://www.snipershide.com/shooting/threads/aerodynamic-jump-with-22lr.6995652/

For a good discussion of wind charts, see https://www.rimfireaccuracy.com/Forum/index.php?threads/a-wind-chart.28674/

If I happend to own a rifle that was exactly opposite of this, would you believe me? I am really serious

 

[Walterfisher]

Not true. If the effect occurs, and almost certainly does, it will apply to all fliers equally. You may not notice the effect on a single shot, but the over all group would move vertically with wind changes.

In this case, my money is on Bryan Litz.

I already agreed that it occurs. It is just hard to see at distances from 100 to 350 m. Go shoot some groups at 300 m with a 22 LR and you will see what I mean. I know who Bryan Litz is.

 

[Walterfisher]

Notice the slope of aerodynamic jump appears flatter at long range compared to short range. The relative flatness of AJ at longer distances would be the reason you don't think you notice it. It's there, but lost in what you perceive as noise.

And this is exactly what I said only in different words.

 

[Suther]

What causes it to raise on a right-to-left wind but drop on a left-to-right wind? Bullet spin, with the assumption it is a right-hand twist?

 

[emerson]

I already agreed that it occurs. It is just hard to see at distances from 100 to 350 m. Go shoot some groups at 300 m with a 22 LR and you will see what I mean. I know who Bryan Litz is.

Your experience lines up with mine. Inconsistency of 22LR ammunition negates the benefit of many precise calculations.

 

[grauhanen]

If I happend to own a rifle that was exactly opposite of this, would you believe me? I am really serious

This would occur with left hand twist rifling.

 

[Longstud]

This would occur with left hand twist rifling.

Precisely, I was sure youd know but thought Id mention it for those who dont realize why. Theyre rare but I owned a rebarelled gun many moons ago and noticed the left twist when cleaning the barrel.

 

[TheWhole9Yards]

Inconsistency of 22LR ammunition negates the benefit of many precise calculations.

This. Its what makes shooting .22LR past 100yards fun, frustrating and rewarding.

 

[grauhanen]

What causes it to raise on a right-to-left wind but drop on a left-to-right wind? Bullet spin, with the assumption it is a right-hand twist?

The following explanation is found here http://www.arcanamavens.com/LBSFiles/Shooting/Downloads/Programs/

Aerodynamic jump. This is Bryan Litz's description of this factor: "Aerodynamic jump is what causes groups to slant when shot in varying wind conditions. Basically, when the bullet exits the muzzle into a cross wind, the bullet tries to yaw slightly to align itself with the airflow. When the bullet yaws to the side, gyroscopic action causes it to nose up or down by a small amount depending on the wind direction. This initial yaw has an effect on the trajectory, and is known as aerodynamic jump. The more severe the cross wind, the more pitch the bullet ends up with. Flying to the target at a pitch angle will result in an elevation error that's proportional to crosswind."

 

[adamg]

Even the physical mechanism used to explain the effect, as referenced in post #19, would suggest that distance should be a parameter in the calculation of the vertical shift. If the bullet is flying nose high, surely it will fly with a different elevation trajectory than flat or nose low, in an amount that stacks up more over longer flight.