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-   -   Oh Boy! Physics! (http://www.firearmstalk.com/forums/f21/oh-boy-physics-75157/)

Vincine 10-27-2012 02:56 PM

Oh Boy! Physics!
 
This is from another forum and concerns .22lr long range shooting. What do you guys here know about this?
Quote:

Originally Posted by Dr_O (Post 4241391)
In addition, if the bullet is of the same size and shape (bullet coefficient) a faster bullet will be negatively affected by the wind more so than the slower bullet. Shooting with a 10 mph. crosswind at 100 yards a 40 gr bullet of the same BC starting at 1260 fps will be blown 5.1 inches off course as opposed to a 1080 fps bullet being blown 3.8 inches.

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?

Overkill0084 10-27-2012 03:02 PM

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...

Vincine 10-27-2012 03:13 PM

Quote:

Originally Posted by Overkill0084 (Post 991813)
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...

Yeah, that's what I would think too.

vincent 10-27-2012 03:15 PM

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...?

Vincine 10-27-2012 03:20 PM

Quote:

Originally Posted by vincent (Post 991831)
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...?

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

jpattersonnh 10-27-2012 03:23 PM

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.

vincent 10-27-2012 03:25 PM

Quote:

Originally Posted by Vincine (Post 991838)
Yes & yes. (How many different twist rates are there for a .22lr?)

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...

Coyotenator 10-27-2012 03:30 PM

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.

vincent 10-27-2012 03:34 PM

Quote:

Originally Posted by Vincine (Post 991838)
Yes & yes. (How many different twist rates are there for a .22lr?)

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...:cool:

lastrebel70 10-27-2012 03:38 PM

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


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