No value winds and how they affect bullets

[Eurodriver]

Common sense says with a no value wind (we will assume for purposes of this thread by no value I mean winds coming AT the shooter at 12:00) you will increase drag on the bullet, slowing it and causing it to drop slower.

That’s what I was always trained to compensate for, am I not correct?

Are there any other variables present on a bullet flying into tough no value winds? Will it cause loss of stability increasing MOA? (unrelated to the round going transonic earlier)

Are there charts or anything to compensate for no value winds?

Editted because I am an idiot.

[Deputy_Dan]

Brother, winds from 3 o’clock or 9 o’clock are full value.

Winds from 12 o’clock or 6 o’clock are no value winds.

[a0cake]

Winds from the 6 and the 12 are commonly called no value winds, not full value.

While head and tail winds are said to have no value, in reality they do have a minor effect.

Conventional wisdom says shooting into a headwind lowers POI. Shooting with a tailwind raises it.

It’s a function of time of flight more than anything else. Remember, two identical objects will fall at the same rate regardless of velocity. A loose bullet simply dropped by hand will hit the ground at the exact same time as a bullet fired at 3,000 FPS on a level plane from the same height.

Since a headwind increases TOF your POI will go down because gravity will have more time to “pull the bullet down.”

How much? A 77 GR SMK out of a MK12, for example, will need ~ 0.3 more MILS of UP elevation adjustment at 1000m with a 20 MPH headwind. (I’m using extreme numbers to illustrate that while there IS a difference, it is very slight.) Use a realistic range and 10MPH wind and you’ll find that you don’t need to worry about it much.

---

^^^ That’s conventional wisdom.

I have my own thoughts. Here they are:

This diagram is something I’ve come up with that IMO is a bit more accurate in certain circumstances.

When you have a Zero where the trajectory of the round crosses above LOS, an increase in the bullet’s TOF on the way to the target (but on the near side of the no wind apogee…which also coincides with maximum ordinate of the trajectory), can actually require HOLDUNDER.

Why? Because until the round hits max-ord, the round is still moving up relative to LOS. Therefore, increasing TOF to a short range target (any range before max-ord) can and does make for a higher, not lower POI. Once the round hits the highest point of the trajectory, revert back to the conventional answer I outlined above and expect to see a lower POI.

All of this is pretty academic though. Unless you’re a competition BR shooter none of it matters much IMO. I don’t believe headwind or tailwind will sufficiently raise or lower POI to any quantifiable or significant level in a tactical environment.

---

Also, here is a better set of rules than thinking using the traditional wind values method, which is actually pretty wrong.

MPH X C = adjusted MPH

If wind direction is 90 degrees from sightline C = 1.0
If wind direction is 65 degrees from sightline C = .9
If wind direction is 45 degrees from sightline C = .75
If wind direction is 30 degrees from sightline C = .5
If wind direction is 15 degrees from sightline C = .25
If wind direction is 0 degrees from sightline C = 0

[Eurodriver]

Wow, I’m not sure how I screwed that up. Thanks DD and a0.

@a0cake

Winds from the 6 and the 12 are commonly called no value winds, not full value.

While head and tail winds are said to have no value, in reality they do have a minor effect.

Conventional wisdom says shooting into a headwind lowers POI. Shooting with a tailwind raises it.

It’s a function of time of flight more than anything else. Remember, two identical objects will fall at the same rate regardless of velocity. A loose bullet simply dropped by hand will hit the ground at the exact same time as a bullet fired at 3,000 FPS on a level plane from the same height.

Since a headwind increases TOF your POI will go down because gravity will have more time to “pull the bullet down.”

How much? A 77 GR SMK out of a MK12, for example, will need ~ 0.3 more MILS of UP elevation adjustment at 1000m with a 20 MPH headwind. (I’m using extreme numbers to illustrate that while there IS a difference, it is very slight.) Use a realistic range and 10MPH wind and you’ll find that you don’t need to worry about it much.

---

^^^ That’s conventional wisdom.

I have my own thoughts. Here they are:

This diagram is something I’ve come up with that IMO is a bit more accurate in certain circumstances.

When you have a Zero where the trajectory of the round crosses above LOS, an increase in the bullet’s TOF on the way to the target (but on the near side of the no wind apogee…which also coincides with maximum ordinate of the trajectory), can actually require HOLDUNDER.

Why? Because until the round hits max-ord, the round is still moving up relative to LOS. Therefore, increasing TOF to a short range target (any range before max-ord) can and does make for a higher, not lower POI. Once the round hits the highest point of the trajectory, revert back to the conventional answer I outlined above and expect to see a lower POI.

All of this is pretty academic though. Unless you’re a competition BR shooter none of it matters much IMO. I don’t believe headwind or tailwind will sufficiently raise or lower POI to any quantifiable or significant level in a tactical environment.

---

Also, here is a better set of rules than thinking using the traditional wind values method, which is actually pretty wrong.

MPH X C = adjusted MPH

If wind direction is 90 degrees from sightline C = 1.0
If wind direction is 65 degrees from sightline C = .9
If wind direction is 45 degrees from sightline C = .75
If wind direction is 30 degrees from sightline C = .5
If wind direction is 15 degrees from sightline C = .25
If wind direction is 0 degrees from sightline C = 0

The bolded is what I was most concerned about. I was shooting out to about 600 yards yesterday in no value winds coming directly at me. I was concerned that in no winds or winds coming from the 6:00 I would be facing a situation where my POI would be higher…but I am not a competition bench rest shooter and an inch, or even a few inches of increased elevation is not an issue at all.

Thanks for the information.

[Deputy_Dan]

a0cake gave you excellent info.

I shoot 6mmBR at Shippensburg PA, and winds there are a bitch most of the time. Clinch River 106gr VLDs help at 600+.

[kartoffel]

@a0cake

Great diagram.

My only suggestion is to consider not the apogee of the trajectory, but the point where the trajectory is parallel to the inclination of the wind. Wind doesn’t always blow horizontally, e.g. say you’re shooting uphill into a headwind coming down the mountain.

[steve_oh]

The B4 next to me says no compensating for no value, blowing in either direction.

And he’s a stone cold killer.

[a0cake]

@steve_oh

The B4 next to me says no compensating for no value, blowing in either direction.

And he’s a stone cold killer.

Yep, and for all intents and purposes he’s right. But sometimes it’s worth it to dive into minutia, if for no other reason than to understand “why.”

[Sgt_Gold]

You would need a hell of a head wind to affect the trajectory of a rifle round. If you’re shooting into that fast of a headwind you better be staked down.

[QuietShootr]

@a0cake

Winds from the 6 and the 12 are commonly called no value winds, not full value.

While head and tail winds are said to have no value, in reality they do have a minor effect.

Conventional wisdom says shooting into a headwind lowers POI. Shooting with a tailwind raises it.

It’s a function of time of flight more than anything else. Remember, two identical objects will fall at the same rate regardless of velocity. A loose bullet simply dropped by hand will hit the ground at the exact same time as a bullet fired at 3,000 FPS on a level plane from the same height.

Since a headwind increases TOF your POI will go down because gravity will have more time to “pull the bullet down.”

How much? A 77 GR SMK out of a MK12, for example, will need ~ 0.3 more MILS of UP elevation adjustment at 1000m with a 20 MPH headwind. (I’m using extreme numbers to illustrate that while there IS a difference, it is very slight.) Use a realistic range and 10MPH wind and you’ll find that you don’t need to worry about it much.

---

^^^ That’s conventional wisdom.

I have my own thoughts. Here they are:

This diagram is something I’ve come up with that IMO is a bit more accurate in certain circumstances.

When you have a Zero where the trajectory of the round crosses above LOS, an increase in the bullet’s TOF on the way to the target (but on the near side of the no wind apogee…which also coincides with maximum ordinate of the trajectory), can actually require HOLDUNDER.

Why? Because until the round hits max-ord, the round is still moving up relative to LOS. Therefore, increasing TOF to a short range target (any range before max-ord) can and does make for a higher, not lower POI. Once the round hits the highest point of the trajectory, revert back to the conventional answer I outlined above and expect to see a lower POI.

All of this is pretty academic though. Unless you’re a competition BR shooter none of it matters much IMO. I don’t believe headwind or tailwind will sufficiently raise or lower POI to any quantifiable or significant level in a tactical environment.

---

Also, here is a better set of rules than thinking using the traditional wind values method, which is actually pretty wrong.

MPH X C = adjusted MPH

If wind direction is 90 degrees from sightline C = 1.0
If wind direction is 65 degrees from sightline C = .9
If wind direction is 45 degrees from sightline C = .75
If wind direction is 30 degrees from sightline C = .5
If wind direction is 15 degrees from sightline C = .25
If wind direction is 0 degrees from sightline C = 0

Brilliant. Possibly too detailed to matter in the real world, but elegant nonetheless. Thanks.

[TiroFijo]

@a0cake

I have my own thoughts. Here they are:

This diagram is something I’ve come up with that IMO is a bit more accurate in certain circumstances.

When you have a Zero where the trajectory of the round crosses above LOS, an increase in the bullet’s TOF on the way to the target (but on the near side of the no wind apogee…which also coincides with maximum ordinate of the trajectory), can actually require HOLDUNDER.

Why? Because until the round hits max-ord, the round is still moving up relative to LOS. Therefore, increasing TOF to a short range target (any range before max-ord) can and does make for a higher, not lower POI. Once the round hits the highest point of the trajectory, revert back to the conventional answer I outlined above and expect to see a lower POI.

One thing to remember in this graph is how exaggerated is the vertical scale compared to the horizontal…

When shooting at 1000 yds with a 308 on a level range the bullet angle of departure with the horizontal is just about 40 MOA, or 3/4 of a degree

This is just a tad more than a 1%, and just about any line of sight in the real world has more vertical angle either up or down.

[a0cake]

@TiroFijo

One thing to remember in this graph is how exaggerated is the vertical scale compared to the horizontal…

When shooting at 1000 yds with a 308 on a level range the bullet angle of departure with the horizontal is just about 40 MOA, or 3/4 of a degree

This is just a tad more than a 1%, and just about any line of sight in the real world has more vertical angle either up or down.

Yep, it’s just a graphical aid to assist in the understanding of a concept. Not to be confused with a realistic representation of reality. M4C has taught me why companies have to put disclaimers on everything. Never assume that something goes without saying, I guess.

[Failure2Stop]

@steve_oh

The B4 next to me says no compensating for no value, blowing in either direction.

And he’s a stone cold killer.

@a0cake

All of this is pretty academic though. Unless you’re a competition BR shooter none of it matters much IMO. I don’t believe headwind or tailwind will sufficiently raise or lower POI to any quantifiable or significant level in a tactical environment.

sigh

[a0cake]

F2S…disagree with my assessment or sighing at steve-oh’s strange reply?

[Failure2Stop]

@a0cake

F2S…disagree with my assessment or sighing at steve-oh’s strange reply?

I wholly agree with your assessment and comment on practical application.

[Reagans_Rascals]

@Deputy_Dan

a0cake gave you excellent info.

I shoot 6mmBR at Shippensburg PA, and winds there are a bitch most of the time. Clinch River 106gr VLDs help at 600+.

Went to College there!

Lived at 26 East Bird St.

Shot mostly down at Caledonia near the reservoir, never did any shooting in Shipp.

but personal things aside, how adversely does a no-value wind, say a head-wind, affect effective range? If there is a 20 mph head wind, how would that affect overall range?

I guess what I’ve getting at is, if you know the overall effective range of your specific set-up and ammunition, you could essentially “cheat” a little more out of it by firing with the wind correct?

I relate it to flying an aircraft. I’ve seen aircraft with ground speeds over mach1, but airspeed’s of less than 450 knots because of a super strong tail wind up in the gulf stream, which gets you there X amount faster with Y amount less fuel consumption.

[a0cake]

Given standard atmospheric conditions of 29.53 inHG, 500 FT EL MSL, 59 degrees F, and 78% humidity…

MK262 out of an 18’’ barrel with 25 MPH (high) winds from:

12 O’clock = Loss of stability at 710M @ 1110 FPS

6 O’clock = Loss of stability at 740M @ 1110 FPS

MK262 Elevation adjustments at 700M from 91M zero:

12 O’clock = 9.1 MILS

NO WIND = 8.9 MILS

6 O’clock = 8.7 MILS

How important is that? Consider that a scope with 0.1 MIL adjustment turrets will move POI 1 CM at 100M, or 7 CM at 700M. If you did not account for either 12 oclock or 6 oclock 25MPH wind in this scenario, your adjustment would be 14 CM off, or just shy of 6 inches.

Important for a Benchrest Competition when shooting off of rock solid platforms? Yes, probably. Important for a Sniper shooting from an improvised position in the field? Not as much.

Keep in mind these calculations are based on relatively extreme wind (which will rarely be perfectly at 12 or 6 oclock) and a relatively anemic round for the ranges at which we’re discussing.

In the end, head and tail winds are at the ass end of conditions I consider before pulling the trigger.

If I have a PDA with a ballistic calculator handy and plenty of time to make a shot, I do input 12 oclock, 6 oclock, and < 5 degree off axis winds. Why not?

But if time is short and I will not be consulting a PDA or data sheet for a firing solution, I do not give consideration to these winds.

You guys can look at the data and make your own determinations for your own purposes.

@Reagans_Rascals

Went to College there!

Lived at 26 East Bird St.

Shot mostly down at Caledonia near the reservoir, never did any shooting in Shipp.

but personal things aside, how adversely does a no-value wind, say a head-wind, affect effective range? If there is a 20 mph head wind, how would that affect overall range?

I guess what I’ve getting at is, if you know the overall effective range of your specific set-up and ammunition, you could essentially “cheat” a little more out of it by firing with the wind correct?

I relate it to flying an aircraft. I’ve seen aircraft with ground speeds over mach1, but airspeed’s of less than 450 knots because of a super strong tail wind up in the gulf stream, which gets you there X amount faster with Y amount less fuel consumption.

[Eurodriver]

A0, really, thanks for all the information.

I sold off my .308 bolt gun because I never shot it anymore but I think I need to get back into the game. I miss all this talk about mils and wind

[a0cake]

@Eurodriver

A0, really, thanks for all the information.

I sold off my .308 bolt gun because I never shot it anymore but I think I need to get back into the game. I miss all this talk about mils and wind

I know dude I’m going through withdrawals myself. Running and gunning Chris Costa style is a hell of a lot of fun (and useful to be good at), but long range is my favorite kind of shooting for sure.

[QuietShootr]

@Eurodriver

A0, really, thanks for all the information.

I sold off my .308 bolt gun because I never shot it anymore but I think I need to get back into the game. I miss all this talk about mils and wind

I spent all day shooting my new FN yesterday. God I missed having a real tackdriver.

Of course, I’m now told by the range commandos that .308 bolt guns are obsolete, so if you want to be super cool you need a .300WSM or something like that. I forgot what shit-talkers the competitive shooting crowd is, at least at the state level.

“Hey, haven’t seen you in a while. New stick? Is that a .300WSM, or a .260?”
“Neither, it’s a .308.”
“Whadja do that for? You’re gonna get your ass whipped at 600, and you can forget about a thousand.”