Instructor:

The other issue long range shooters don't generally consider is the impact of mirage itself. Mirage is light refraction and displaces the target image in the direction of the mirage. Thus, when the mirage boils, it is actually making the target appear higher than it actually is.

As for the left rifling question, you are right: it would have the opposite effect.

My click rule above is just a swag at the vertical displacement only, not the horizontal drift. Like I said, last week I held anywhere from 2 to 6 MOA; once you start holding over 4 MOA, it gets really tough to plant that bullet within five inches of where you are aiming. At least for me it is on the first shot (a sighter obviously makes a huge difference). And of course, once in a while you can get fooled by a wind that appears relatively calm. I try and always looks at vegetation to get some idea of the strength of the wind. I also look to see how vegetation near rocks or other wind blocks are moving.

What do think of these two videos (you may have to skip ad, if you want). Both deal with wind corrections.

https://www.youtube.com/watch?v=hBdhWe-C4Co

https://www.youtube.com/watch?v=hHxhIZHUUsA

I should have mentioned that a mirage "boil" does as stated and especially with micrometer/iron sights a river like mirage image will tend to move in your mind's eye either right or left and cause you to focus more to one side or the other. Obviously the target face did not physically move but it appears to have moved, plays tricks on your eyes. The one video mentions using higher performance cartridges as the 7mm Rem. Mag. or 284/6.5, etc. and no question they have an advantage over the lowly 308 but if you are routinely putting 3-5000rnds/year in match shooting the barrel life on those superior rounds is considerably less, near half the life. Economics comes into play since quality match grade barrels installed will run 6-$800.00 per. Usually can get near 3000rnds on a 308 before it starts going south opposed to 1500 for the "hotter" cartridges. Have observed frequently during a long hot match day those shooting the stronger cartridges begin to falter due to the recoil and fatigue. Some do it very well, but more than I wanted to endure. Rule of thumb, can get some 150rnds/1lb. of powder for the 308 and can't get there with the hotter rounds. The bullet selection as mentioned is critical but the 168SMK is not the one you want to use at beyond 500yds. For Palma shooting the lightest one I used was the 175SMK and more often used the 190SMK. It is still supersonic at 1000yds, barely, but it will do the job. Just some thoughts.

I have no knowledge myself but there was a program on TV the other day where the "instructor" talked about the kestrel 4000.
FWIW.
Peter

quote:

Originally posted by Ackley Improved User:
What do think of these two videos (you may have to skip ad, if you want). Both deal with wind corrections.

https://www.youtube.com/watch?v=hBdhWe-C4Co

https://www.youtube.com/watch?v=hHxhIZHUUsA

First video:
That is pretty much how I do it with the exception of using a wind flag on my spotting scope. But I judge wind exactly the same way.

Second video:
You are kidding right? By the time you get done dinking around with that thing the sun has set or at the very least the wind has changed. Even if you have time to enter all that stuff, how do you know the speed 400 yards away? And even then, when TOF gets long, wind changes while the bullet is in flight...and this guy is talking about wind drift in tenths of an inch??

This is a pretty good video; I have often written that wind is like mending a fly line - the current is always faster on the surface than on the bottom.

His spiel on shooting in canyons is spot on: I have said the same thing on AR many times.

I would say the stuff on Cosine is a bit too complicated when it comes to calculated wind. Instead of the cosine of the angle, take the wind angle, divide by two, then add that back to the angle and round up to the nearest five subject to a maximum of 90. This is the percent full value. For example, half of 45 is 22.5; add that back to 45 is 67.5, which rounded up is 70 percent, or .7, almost identical to the cos(45). A 30 degree wind (which is a 7 oclock wind BTW) goes like this: 30/2=15...15+30 = 45. Round up to the nearest five = 50 percent, or .5, which is the same as cos(30).

https://www.youtube.com/watch?v=efd1kLsvjFA

AAZW,

Suppose you're shooting 800 yds across a canyon ~500 ft deep below you, and you measure the wind with your hand-held Kestrell at 7 mph at 3:00. It's late morning, but that big Coues deer just stepped out at 800 yds from behind the Mesquite tree you've been looking at for over an hour but seeing nothing.

How would you use your spotting scope and much wind correction would you use?

Not sure if your deer is in the canyon requiring consideration for shooting down hill or not, but if target on basically the same level as the shooter would put something slightly less than 6moa of wind adjustment. If target is at lower elevation as in 500' then would have to adjust accordingly. In caliber range of 308, 30-06 and at 800yds. would have some 25moa elevation from my 100yd zero IF target on same elevation as the rifle. This works for me on paper targets and have no experience shooting at game for this distance other than ground hogs, crows, etc. Late morning may have the sun producing heat by then and would have to be aware of any mirage "boils" visible through the scope and would add that if seeing mirage while observing target and it suddenly went away, would hold up for wind speed increased.

quote:

Originally posted by Instructor:
Not sure if your deer is in the canyon requiring consideration for shooting down hill or not, but if target on basically the same level as the shooter would put something slightly less than 6moa of wind adjustment. If target is at lower elevation as in 500' then would have to adjust accordingly. In caliber range of 308, 30-06 and at 800yds. would have some 25moa elevation from my 100yd zero IF target on same elevation as the rifle. This works for me on paper targets and have no experience shooting at game for this distance other than ground hogs, crows, etc. Late morning may have the sun producing heat by then and would have to be aware of any mirage "boils" visible through the scope and would add that if seeing mirage while observing target and it suddenly went away, would hold up for wind speed increased.

Sorry, this answer doesn't help me much - I don't know what your BC and muzzle velocity are.

Please indicate how much wind in mph you're holding for, and are you considering variable or constant windage across the canyon. If it's 7 mph at your FFP, what is it mid canyon?

Also, how are you reading the mirage for wind in mid flight or for target position distortion, etc.

quote:

Originally posted by Ackley Improved User:

quote:

Originally posted by Instructor:
Not sure if your deer is in the canyon requiring consideration for shooting down hill or not, but if target on basically the same level as the shooter would put something slightly less than 6moa of wind adjustment. If target is at lower elevation as in 500' then would have to adjust accordingly. In caliber range of 308, 30-06 and at 800yds. would have some 25moa elevation from my 100yd zero IF target on same elevation as the rifle. This works for me on paper targets and have no experience shooting at game for this distance other than ground hogs, crows, etc. Late morning may have the sun producing heat by then and would have to be aware of any mirage "boils" visible through the scope and would add that if seeing mirage while observing target and it suddenly went away, would hold up for wind speed increased.

Sorry, this answer doesn't help me much - I don't know what your BC and muzzle velocity are.

Please indicate how much wind in mph your holding for, and linear or constant across the canyon.

Also, how are you reading the mirage for wind in mid flight or target distortion, etc.

AIU:

It is impossible to answer to answer your question...what is the wind doing on the other side of the canyon? Can you detect mirage mid-way across? What kind of tree movement are you seeing on the other side? Are you in the open on the canyon or are you somewhat sheltered from the wind?

I can take a guess at one thing: the wind is going to be blowing a lot more in the middle of the canyon than 7 mph - I would say twice as much would be a good guess.

Personally, I would take a rock shot (assuming I have not practiced shooting in this canyon). If the deer bolts, so be it, but in my experience he won't as long as the rock isn't right behind him.

By mentioning 308, 30-06 calibers with velocities in 2500fps to 2800fps would be the ones I am referencing(ones I have most experience with in shooting at long ranges.)
Approach I am familiar with in doping the wind is that you estimate for the first 1/3rd or 1/2 of the range to target and that is the area that the most impact wind has on the flight of the bullet, it's course/path has been determined when reaching that distance. Example you gave is a full value wind,7mph/3 o'clock(800x7=5600/1000=5.6moa adjustment) perpendicular to the flight of the bullet which imparts most deviation of that flight opposed to 1/2 value or say from 2 o'clock to 8 o'clock. I would not attempt to adjust for wind at the target. If the tree limbs, brush, weeds, "dust devils," etc. reflecting strong wind, would not take the shot in that situation.
A sight in shot or "rock" shot is an approach to confirm or not confirm your estimate, but likely to spook the game?? Method I use for determining mirage, at say half way, is to simply back focus your spotting scope to that area and you would have a grasp of what is going on there regarding mirage. As for the Kestrell device or similar ones, I have no experience with them in my shooting but if works for a hunter, that's a good thing.

quote:

Originally posted by Instructor:
By mentioning 308, 30-06 calibers with velocities in 2500fps to 2800fps would be the ones I am referencing(ones I have most experience with in shooting at long ranges.)
Approach I am familiar with in doping the wind is that you estimate for the first 1/3rd or 1/2 of the range to target and that is the area that the most impact wind has on the flight of the bullet, it's course/path has been determined when reaching that distance. Example you gave is a full value wind,7mph/3 o'clock(800x7=5600/1000=5.6moa adjustment) perpendicular to the flight of the bullet which imparts most deviation of that flight opposed to 1/2 value or say from 2 o'clock to 8 o'clock. I would not attempt to adjust for wind at the target. If the tree limbs, brush, weeds, "dust devils," etc. reflecting strong wind, would not take the shot in that situation.
A sight in shot or "rock" shot is an approach to confirm or not confirm your estimate, but likely to spook the game?? Method I use for determining mirage, at say half way, is to simply back focus your spotting scope to that area and you would have a grasp of what is going on there regarding mirage. As for the Kestrell device or similar ones, I have no experience with them in my shooting but if works for a hunter, that's a good thing.

Thanks, this detail is more helpful. Regards, AIU

This is very.interesting reading. I have to re read it several times to "get it " beings this is only my 2nd summer emphasizing long range marksmanship I have tons to learn. I've never even been to a high power or long range match. . I typically don't have a lot of mirage issues as most places the permafrost isn't too deep and so the ground is cool. But wind, I have plenty of that. I'm glad I'm starting with the 6.5 Creedmoor. Not that expensive to learn with. .

As to the Kestrel's which one would be the best for a first time buyer that probably won't be shooting over 1,200 yards at rocks or cut banks. ??
My fon is an Android and I don't plan to go all electronic teck. Being on an internet forum is about the height of my puter skills.
I can manage JBM ballistic calc with some challenge. But I do get the information I think I need. .
Thank you.
Glen.