Shooting across canyons/ bullet drag

[ID_Matt]

One of my local ranges for PRS and NRL hunter matches is right on the snake river canyon in southern idaho. It is amazing to see the effects of updraft there. Depending on range, as much as 0.4 mil. People who have never shot there are usually at a disadvantage and miss high all day. You can't feel any wind where you shoot from but if you walk to the rim and throw some grass or something off of it, it shoots straight up back towards you.

 

[TaperPin]

Yesterday while shooting a few mock nrl hunter stages we set up, me and a buddy were noticing that at the far targets our shots were trending high.

At first when the wind was sub 10 mph right to left we both had to adjust 0.2 down, later in the day when the wind picked up it was as much as .4-.5

Now, both of our rifles/loads have been trued and there was no doubt in either of our systems inputs or zeros, so we make sure pressure/ DA was true with a kestrel and again it was correct.

The only other explanation is the terrain. The far targets were across a steep canyon that had a significant vertical updraft.

We both have shot across canyons many times, but in this terrain it had the most notable effect. It's a long valley, and this canyon ridge is the first wind break coming up from the valley floor. So I'm thinking that without any other features to create turbulence or slow the wind down, that updraft is pushing the bullet travel upwards significantly.

Sub 650 yards, the effects were marginal, but once we got out to 800 and beyond it was substantial.

Anyone else experience this updraft on bullet flight when shooting over steep canyons? I'm used to horizontal winds doing weird things over canyons and in mountainous terrain, but the vertical aspect had never been as pronounced as it was for us yesterday.

It was good though, I like learning these things while practicing and training, as it really makes me think about my limits on game depending on environmentals

Sounds like a fun practice spot. Lots of good suggestions already.

 

[Wrench]

I use a kestrel to get the wind speed and that is all. I find that if I use it as a solution, I screw it up more than not. If I get a speed I input it for 90* and then work it out from there based on the compass. My rule of thumb is to always err on the side of the impact.....I want to be closer to hair than not. I personally over correct for wind much more than under.

 

[wind gypsy]

You're looking for any clues. Debris, dust, mirage.....you can see a lot of clues once you know what to look for.

Yeah, Im usually hoping for some kind of particles in the air so I don’t have to count on my non-existent mirage reading skills.

 

[WKR]

Yes, wind flows like water. Wind going up a hill/canyon has as much effect as if it were blowing from the side. The hill angle and your angle means it won’t be a full value wind, cause it will be coming in at oblique angle.

And, as right to left wind you got a little aerodynamic jump at 850 as well.

That was our first thought that it was AJ, but it was more than normal.

I like the wind flows like water analogy

Based off our dope from that day and wind speeds we were seeing, we made this "uplift" range card. With a 10" deer sized vital being the target size.


And this is just based on the dope we were witnessing that day with those specific environmentals.

 

[E.Shell]

When I used to shoot the Allegheny Sniper Challenge, we had a target at the top of a big gully. On a breezy day with the wind coming up the gully, bullets were often deflected upwards by 2 feet or more at 950 yards.

 

[WKR]

You're looking for any clues. Debris, dust, mirage.....you can see a lot of clues once you know what to look for.

Sometimes.... sometimes out here in the high desert it seems like nothing moves and the grasses at the target are too far to see. Sage brush can help if the wind is really strong.
Mirage is all I got at times.

 

[hereinaz]

That was our first thought that it was AJ, but it was more than normal.

I like the wind flows like water analogy

Based off our dope from that day and wind speeds we were seeing, we made this "uplift" range card. With a 10" deer sized vital being the target size.


And this is just based on the dope we were witnessing that day with those specific environmentals.

View attachment 833408

I believe it. The angle of the hill can make a difference too.

Did you account for a 6 o’clock tailwind wind in the original dope?

Tailwind plus the vertical wind matter.

Also, what was your shooting angle? Were you shooting steep up a hill?

 

[WKR]

I believe it. The angle of the hill can make a difference too.

Did you account for a 6 o’clock tailwind wind in the original dope?

Tailwind plus the vertical wind matter.

Also, what was your shooting angle? Were you shooting steep up a hill?

Not quite 6 o'clock but yeah I did account for the angle in which the wind was blowing in relation to the target. Which it was a tailwind just not full value.

No, shooting angle was actually slightly down hill to the 800-870 yard targets. Shooting position 1 was about 5100' and target was at 4950' across that canyon and position 2 was damn near 0° angle.

 

[hereinaz]

Not quite 6 o'clock but yeah I did account for the angle in which the wind was blowing in relation to the target. Which it was a tailwind just not full value.

No, shooting angle was actually slightly down hill to the 800-870 yard targets. Shooting position 1 was about 5100' and target was at 4950' across that canyon and position 2 was damn near 0° angle.

I say that because shooting at a steep angle up causes shots to go high because the effect of center of gravity, inertia and the changes in recoil.

 

[Lawnboi]

Reading terrain is just as important as speed, and direction.

 

[WKR]

I say that because shooting at a steep angle up causes shots to go high because the effect of center of gravity, inertia and the changes in recoil.

Understood,
Earlier you mentioned at times you will take .1-.2 off your dope. Is that dependant on range and terrain?

 

[Flyjunky]

Sometimes.... sometimes out here in the high desert it seems like nothing moves and the grasses at the target are too far to see. Sage brush can help if the wind is really strong.
Mirage is all I got at times.

High desert can be tough. Sage and juniper are very stiff and can be tough to get a reading off of.