Is it the Wind or Something I'm Doing?

[scsims]

I conducted the "Tall Test" from Bryan Litz's new book today on my .243. I was happy to see that my POI stayed perfectly vertical with 30" of elevation adjustment. My Nikon Monarch had traveled 34.25" for the 30" of adjustment.

Then I was doing some testing/practicing at 300 yards. I had what I though was a full value wind from right to left at 5 mph, so I adjusted the windage for 1 MOA as directed by JBM. I shot 3, and went to look and I had hit a .5 MOA group about 6" to the right of the intended POI. I thought this can't be right. So I settled back on the 100 yard target. Shot center about 3" high because I didn't change my elevation turret back. So all looks good, I shoot 3 more at 300 and the same thing. So I start thinking is the wind doing something different than it appears here where I'm at? I can see down range at my pond the wind is definitely moving in the same direction. So I keep looking around and notice that in front of my house which is higher in elevation the wind was blowing the opposite direction.

So is it possible that the air aloft... say 20ft above the ground where my bullet spends about half the distance traveling to the target is actually moving in the opposite direction?

I adjusted for left to right wind and it was on. It's just frustrating......

 

[Joe King]

I bet your canting your rifle. I'm horrible about that, a scope level is the only way I've been able to correct it.

 

[kcebcj]

How did it shoot with no adjustment? Look at the trees around you and you will probably see that the air is moving in the same direction at the top of the tree as it is at the base or in the grass. Did you guess the wind correctly or use a meter? Did the wind come and go and you shot when it was still?

With good shooting skills it still takes a lot of practice to get the wind right. Good luck

 

[ajhardle]

Most of the time I have a question like this, it leaves me frustrated all week until I make it out shooting again and realized what a bone head I am. (Not that I think you're a bone head.)

 

[long450]

I bet your scope is not aligned with the bore. You can check by marking a 3 foot line on a target with a verticle level or plum bob. Start at the bottom and confirm zero then add ten minutes and shot 2 shots. Do it again atat ten more minutes. If the scope is aligned properly your impacts will be on or near the line, if not they will wander off to the right or left. Do this at 200 yards.

 

[WildRose]

I bet your scope is not aligned with the bore. You can check by marking a 3 foot line on a target with a verticle level or plum bob. Start at the bottom and confirm zero then add ten minutes and shot 2 shots. Do it again atat ten more minutes. If the scope is aligned properly your impacts will be on or near the line, if not they will wander off to the right or left. Do this at 200 yards.

A slight cant in the rifle will do the same thing.

Need to both check the scope level relative to the rifle as well as checking to make sure the rifle is being held level.

As to the Op's question it could be the wind is changing on you between you and the target or it could be the above.

There is nothing harder to master than reading the wind. Pretty much every other variable can be accounted for with modern ballistic software and good marksmanship.

 

[scsims]

It's possible that I'm canting rifle itself as I do not have a level for it. But I believe that I eliminated the scope cant and alignment with the bore with the "Tall Test" the same test as described by long450.

I will put a level on the scope and try again today and post the results.

 

[paphil]

The scope is the only thing that has to be vertical. The cant of the gun matters very little as long as the scope remains vertical and point of impact changes will not be discernable at all to most shooters. That said, the scope must be vertical as possible, each degree of SCOPE cant will move POI about 3 inches at 1000 yards. Spin drift will be about 8 to 10 inches at 1000 yards. It takes a very accurate rifle and a very good shooter to discern these variables at long distances. That is why the 100 yard vertical test is so important. Anyone who says the gun must be perfectly verticle with the scope has never seen Dave Tubbs guns! Some scopes are several degrees out of vertical, even when the cross hair is perfectly alligned with the vertical line drawn on the target. It is due to construction errors or tolerances at the factory. Just about every person I know that looks through a vertical gun and scope for the first time will say that it is crooked! Everyone has a "comfortable" way they hold their gun. The best way to level the scope is while the shooter is holding the gun in a comfortable position. Before anyone out there trys to discredit this, go try it . Rotate a scope 10 or 15 degrees and shoot a vertical group with the scope held vertical. I've done it. It works! As for the wind. keep practicing!

 

[ajhardle]

Rifle cant? 6" at 300 yards? That would be tilting the gun 30 degrees or so.

I would leave that windage knob alone for a little while, and just hold for wind along the horizontal crosshairs.

 

[scsims]

Just tried 3 more shots from a rock rest and had the same result. Then 3 from a bi pod and the group was not as far right and tighter. I'm about to try 3 prone.

BTW no wind this morning.

 

[scsims]

Prone was the best, actually was center of the point of aim. So I guess this tells me that I suffer from technique problems??

 

[scsims]

I'm just lost!! Not sure what's going on here. I realize that I do have something going on with my form, as I tend to hit a little to the right with my 308 as well, but why am I dead center at 100 and then to the right at 200 and 300? The Tall Test eliminated scope alignment and cant I use a level on my top turret to verify that I'm shooting level.

Please look at the target and tell me your thoughts. It's at 300 yards and the one to the far right was a fouling cold bore shot. I had some oil left in the bore. I piled most of them together but 2 are at the point of aim.

When shooting at 300 yards the last 100 yard of bullet flight travels through a narrow lane of tall pines. Could this affect anything? I don't think so, but I thought I'd toss it out there.

 

[8andbait]

I like my POI set about 1/2" left at 200 yards for a left to right twist. Opposite for right to left twist. I would wait for a day with NO wind and attach a level to eliminate cant. Then try it at 300 without adjusting the windage and see where it lands. Nothing is as frustrating as the wind.

 

[ajhardle]

Did you dial out parallax?