# Oh Boy! Physics!

Discussion in '.22 Rifle/Rimfire Discussion' started by Vincine, Oct 27, 2012.

1. ### VincineNew Member

This is from another forum and concerns .22lr long range shooting. What do you guys here know about this?
So the rotational speed of a bullet interacting with a side wind has a larger effect on its trajectory than the amount of time a bullet is subjected to the side wind??

Higher speed bullets have a flatter trajectory than lower speed bullets. Under 'No Wind' conditions, the higher speed bullet will be more 'accurate'. That is, it requires less adjustment of POA than a slower speed bullet.

This implies that there is a wind speed/bullet fps crossover point at which the flatter trajectory of the higher speed bullet is negated by the effect of a side wind. Right?

2. ### Overkill0084Well-Known Member

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No math on my side of this, I nearly flunked physics. But it seems to me, that the faster the bullet moves the less time ANY outside force gets to act on it, be it wind, gravity or other.
Great, now my head hurts, thanks a lot
Perhaps a math whiz will be along shortly step all over this...

Last edited: Oct 27, 2012

3. ### VincineNew Member

Yeah, that's what I would think too.

4. ### vincentNew Member

Wouldn't differing twist rates come into play here as well or is this a question with constant factors with wind speed being the only variable...?

5. ### VincineNew Member

Yes & yes. (How many different twist rates are there for a .22lr?)

6. ### jpattersonnhWell-Known Member

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I just ran the numbers through a ballistics calculator, strange!
40gr at 1080mv w/ 10mph cross wind will be 2.3" off at 100 yards, 16.1" at 200 yards
Same bullet traveling 1260mv at 100 yards is 2.9" off at 100 and 11" at 200 yards.

It must have something to do w/ when the bullet goes subsonic. I guess that is why match ammo is subsonic.

7. ### vincentNew Member

Not sure...I'll look into it...

Was thinking of things from a baseball perspective, curveball vs fastball vs knuckleball. All have different spins and all have unique movements from interacting with the air...

8. ### CoyotenatorMember

The whole point of gyroscopic stabilization, is the rotation causes the projectile to resist being deflected from it's trajectory, so a faster rotation should result in less deflection from the wind.

9. ### vincentNew Member

A quick googling says quite a few, anywhere from 1 in 9 to 1 in 16 (maybe more?) which makes sense since different grains call for different twist rates...

10. ### lastrebel70Member

Where is Zombiegirl for all of this? She is a math teacher after all.

11. ### VincineNew Member

I don’t think we’re talking about sideways wind drift. I think we’re talking about a lifting or ‘sinking’ effect depending on the direction of a bullets rotation, 'clockwise' or 'counter clockwise' and whether the wind is coming the bullet’s left or right.

Last edited: Oct 27, 2012
12. ### VincineNew Member

I found something. It's called the Magus Effect:http://en.wikipedia.org/wiki/External_ballistics (Scroll down)

It says, "The Magnus effect has a significant role in bullet stability because the Magnus force does not act upon the bullet's center of gravity, but the center of pressure affecting the yaw of the bullet."

But (However?) http://en.wikipedia.org/wiki/Magnus_effect#In_external_ballistics
says,"Overall, the effect of the Magnus force on a bullet's flight path itself is usually insignificant compared to other forces such as aerodynamic drag. However, it greatly affects the bullet's stability, which in turn affects the amount of drag, how the bullet behaves upon impact, and many other factors."

I know a .22lr is a way to experience the challenges of Long Range Shooting in ‘miniature' and at considerably shorter distances, but now I think I’m sorry I brought this up.

13. ### mrt8110New Member

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physics

I got an Idea,Try different and speeds and see what happens.... BTW, I only shoot sub-sonics. Therefore I do not have to worry about all this physics marlarky. Cliff!

14. ### pranc2New Member

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it is the trans sonic flight of the bullet that effects it the most. pressurized air builds up in front and pushes the bullet around more. since .22lr dont go way pass the speed of sound and you have lower bullet weight it is more noticeable. the speed of sound depends on outside temp. elevation and humidity. this is why all match grade .22lr is sub sonic... and like many of you said rotation also plays a role like a frisbee in the wind.

you can look at sonic booms and the cloud that you see is pressurized water vapor and the same thing is happening to our little bullets.

Last edited: Oct 27, 2012
15. ### Flat TireActive Member

I know the sub sonic ammo is more accurate at long range than the faster ammo. It has something to do with not breaking the sound barrier. I think when a bullet goes faster than 1050 and then slows below 1050 it becomes worthless and in some cases starts to tumble.

16. ### VincineNew Member

I'd give you full credit.

As a high speed .22lr bullet slows down, and the pressure wave ‘catches up’ to the bullet, it causes an abrupt increase in the air pressure the bullet it traveling through and the bullet can begin to yaw, destabilizing it. After it has gone through the ‘trans-sonic’ area it may, or may not, regain sufficient stability to continue to the POA.

If you’re shooting a hyper velocity bullet at a short range, it’ll hit the target before it slows down to the transonic speeds and you’re good. If you’re shooting a real heavy larger caliber bullet, with a lot of mass, out of a high twist rate rifled barrel, going a lot faster to begin with, it is affected less.

If you’re shooting a .22 high velocity, you’re good to about 70-80 yards, and then your groups will open way up. Or at least that’s where mine do. I’m at 1500 ft above sea level and speed of sound here is about 1095 fps.

If you use slower sub-sonic bullet to begin with, it's not a problem. You'll have a lot more drop, but that's a constant that can be accommodated with elevation.

You’ll need this for the test.

Last edited: Oct 28, 2012
17. ### JTJWell-Known MemberSupporter

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You also have to keep in mind that 22lr bullets have a really bad design and ballistic coefficient. The 17HM2 is a necked down 22lr with a lighter bullet has a much better shape, ballistic coefficient and will stay supersonic out to 100 yards or more. It is however affected by wind and costs twice as much as good 22lr HV ammo. The HV 22lr should realistically be held to a max of 70 yards.

18. ### partdeuxWell-Known MemberSupporter

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Sounds like a really complex calculation with some significant outside influences!

Spinning bullet will tend to avoid tumbling, tumbling bullet will be greatly influenced by wind.

Don't even pretend to understand the dynamics between supersonic and subsonic and especially the transition from one to the other.

Longer the bullet it's in flight, given none of the changes above, the more the force will impact the path... but those changes will make it a much more complex calculation, way beyond my pay grade

19. ### EturnsdaleNew Member

My experience with ballistics is moreso with terminals than externals. So please forgive me if I am not getting this.

A bullet fired at 1020 ft.sec from a rifle with a 1 - 16 twist will rotate completely once every sixteen inches. A bullet fired at 1270 from a rifle with a 1 in 16 twist will rotate completely once every sixteen inches. So are yall saying that it rotates faster only because it takes less time to travel that sixteen inches?

20. ### ChainfireWell-Known MemberSupporter

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If it does, it does. If it don't it don't. I don't need to know why, I am a Democrat.

Just allow for drift on the second shot............