This may have come up earlier. If it did I missed it. I have a real nice looking chart on bullet impact for different wind directions. There is no scale to it and therefore of very little value to me.

Some people seem to think that a tail wind or a head wind has quite an effect on the bullet but I'm not convinced that is true. In my feble mind, I think that a 10 mph head wind will only make the bullet drop about 1 min, or 1 inch at the rams. I have no proof of that at all, can any of you guys help me out or at least point me in the right direction.

The sideways is easy but vertical has me stumped.

i guess it becomes a matter of what folks consider significant. Given the Ram is only 2moa high, a one minute drop due to a 10mph head wind is something I would pay attention to. What that says is if you break a shot just a tad below dead center your shot will drop between the legs. Got to keep your shots center to high center in that condition. Same challenge with no wind but a heat boil. Depending upon the boil, you can break a shot dead center and miss over the top. You have to break your shots low.

Now... here in Washington we don't permit such conditions to exist. Just flat out not allowed. Constitutional Amendment if i remember correctly...

Dave, I see people in western WA go into full panic mode when the wind flags flutter. It's a joke, OK.

Menawhile, you are right about 1 min being a factor. I still don't know if that is a good number. It is just about impossible to get the wind to help me out in testing the effects.

Draw the line when winds hit 30 MPH - stirs up so much grit that cleaning it out of your gear takes days.

So will a 10mph wind from behind you lift the bullet 1 moa?

it is difficult to do practical testing because you have to be certain of the wind speed and value... if the wind is quartering to any degree you will lose valuefor the vertical drop. then how often do we shoot in a perfectly consistent 10mph wind with no pulses, gusts, or drops. tough to prove out. and... we don't freak out when the wind flags flutter. we don't use wind flags! they are only put up when outlanders are expected for company.

Slowstdy, That is what I am trying to figure out. I think so but I'm not sure.

I guess I am getting bord and I am looking for something else to learn about.

I found an article by William T McDonald from Sierra on this subject and below is his conclusion.

....... vertical drifts due to the yaw of repose cannot be calculated because the necessary a very expensive laboratory instrumentation. Luckily, the drifts are small compared to the (wind) deflections.

It looks like it is all trial and error to get the information.

A 10 mph wind is also 15 ft/sec. Assuming the bullet is traveling at 1050ft/sec., a direct headwind will change the ground speed of the bullet by about 1.5%. The time in the air to the rams is pretty short (1/3 sec or there about) so 1.5% should have almost no effect on the POI. All of the above assumes laminar flow air parallel to the ground which never happens.

Because airflow is always turbulent the drop on the projectile is most likely caused by the bullet passing through turbulent air. Even at 10 mph the tumbling of the air can impart a significant and sudden force on the bullet. The bullet will also pass through many transition zones as the air mixes and upset the stability which will impart more drag onto the bullet causing the drop.

There are a few good freeware programs that figure ballistics and find one you like and plug in different muzzle speeds based on the wind and see what happens. The airspeed of the bullet never changes, just the ground speed or time to impact.

A chart is helpful but not as much as a good spotter or shooting paper at the start of the match. Depending on how the range is constructed, the amount and effect of turbulence is going to change as you move across the firing line. During zero, don't stand in one spot at one distance. If you are able, shot paper at each animal location and note what changes.

Having said all of this, a decent wind also moves the shooter quite a bit which I believe has a greater effect on the POI than the wind acting on the bullet during flight. Best way to become good in windy conditions is shoot in windy conditions and take notes.

It appears to me that the vertical displacement of a bullet because of a head wind or a tail wind will not take the average shot out of the normal group unless you are shooting in a way too strong wint to be shooting in.

The subject was a brain teaser to me and I have heard many people on the line make verticle corrections for wind.

Horrizontal corrections is another matter alltogether. Most of us have trouble judging wind speed so it all becomes trial and error but the corrections have to be made.

Jerry;

I don't have any laboratory data for you but I do have some qualitative results.

March of 2007 I shot a 200m smallbore silhouette match in Soda Springs. It was a lot of fun. It was cooked up by the black powder shooters from what I hear. Two fifths targets at double the smallbore distances. Offhand for chickens and prone for all the rest. One really big difference, 10 minutes for sighting and shooting all your targets! That works only if you already know your come-ups which I didn't!

March in Soda Springs, ID is brisk and the match proceeded in 30 degree weather with wind gusting up to 35 mph and swinging from SE to NE. Since the range faces south that puts the wind quartering on to quartering behind. I was able to sight in during a lull but the wind came up and the results....you'd just have to laugh.

With the wind quartering on, I would hold left off the tip of the ram's muzzle (from prone shooting a Pearson 581 with a Weaver T24) and watch the bullets go through the legs. With the same hold and the wind quarting from behind the bullets would go over the back. Holding off and high or low depending on the wind helped but if the wind was different down range than right at the line, well you just had to laugh because cussing didn't help.

I did pretty well that day but the match winner was shooting a rebuilt Ballard with Soule type sights! Damn, that's good shooting!

Anyway, there's some results. I watched carefully and yes, wind does have some effect, especially when the wind is strong, the range long and the bullet is as aerodynamic as a .22.

dwl

I found a chart on Team40X but I don't know how correct it is.

Direction---Hit Location

12:00-Center and Low about .2 min
01:00-Left 1.2 min and High .2 min
02:00-Left 3.7 min and High .7 min
03:00-Left 4.4 min and High 1.0 min
04:00-Left 3.2 min and High .8 min
05:00-Left .7 min and High .3 min
06:00-Center and High about .2 min

It doesn't tell the distance or the wind speed.

Jerry G wrote:This may have come up earlier. If it did I missed it. I have a real nice looking chart on bullet impact for different wind directions. There is no scale to it and therefore of very little value to me.

Some people seem to think that a tail wind or a head wind has quite an effect on the bullet but I'm not convinced that is true. In my feble mind, I think that a 10 mph head wind will only make the bullet drop about 1 min, or 1 inch at the rams. I have no proof of that at all, can any of you guys help me out or at least point me in the right direction.

The sideways is easy but vertical has me stumped.

1 MOA at the 500m ram line will be about 5.38 inches, and not 1 inch, 1moa at 100 yards is 1.047" take another look at my posts in the changing zero thread.... i touched a little bit on this

Ky,
we're in the 22 ammo forum, remember?