Feedback: 6.5mm Wind Drift Data

[Das Capitolin]

This past season was my first with the new Savage 12 LRP, and so now that my load is developed with applicable drop rates I am collecting wind drift data. Here are the wind values I calculated. It's difficult to record conditions and settings during the match, so I'm stuck with using calculators based on my drop data. Perhaps someone with a similar load can share their wind drift data for comparison?

Savage 12 LRP in .260 Remington with 26" barrel
6.5mm 140gr Hornady BTHP Match bullet, 42.0gr H4350, Remington brass

Yards | Elev. | 3-wind | 5-wind | 7-wind | 10-wind
220 = 0.5 mil | 0.1 mil | 0.2 mil | 0.2 mil | 0.3 mil
420 = 1.8 mil | 0.2 mil | 0.3 mil | 0.5 mil | 0.7 mil
550 = 2.7 mil | 0.3 mil | 0.4 mil | 0.6 mil | 0.9 mil
665 = 3.8 mil | 0.4 mil | 0.6 mil | 0.8 mil | 1.1 mil
860 = 5.6 mil | 0.5 mil | 0.8 mil | 1.1 mil | 1.5 mil

[postal]

AR15Barrels might be able to help you. I know a few guys run 260 in here...

Though, all the data you gave, you did not give a velocity.... thats key....

But have you checked other ballistics programs? google 'jbmballistics' it'll turn right up- plug in the numbers and its pretty good- and free.

[Bete Noire]

If you read Bryan Litz's book on applied ballistics, he seems to believe the calculations should be pretty darn accurate. Using chrono data, G7BC, twist rate, etc it should be damn accurate.


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[ar15barrels]

This past season was my first with the new Savage 12 LRP, and so now that my load is developed with applicable drop rates I am collecting wind drift data.

You are doing it wrong.
Go shoot.
Note the wind speed with a handheld meter.
Note the wind conditions between your firing point and target and compare them to your firing point.
Fire at the target.
Note the amount of wind drift.
Learn to work from a 10mph 90 degree wind as "full value" and how to value angles and speeds to the standard 10mph "full value" figure.
No need to worry about 3mph or 5mph or 7mph drift as those are just "pieces of the pie".
Only the full pie and the "value" of the wind matters.

Do that enough and you will just KNOW how much wind to hold in specific conditions.
Wind changes so fast that by the time you look at your chart and figure out how much wind you need to hold or dial, it has already changed.

Mirage is your best instant indicator of the total wind conditions.
Learn to read mirage.
Learn how to hold-off based on mirage.

[Das Capitolin]

AR15Barrels might be able to help you. I know a few guys run 260 in here...

Though, all the data you gave, you did not give a velocity.... thats key....

But have you checked other ballistics programs? google 'jbmballistics' it'll turn right up- plug in the numbers and its pretty good- and free.

I already have drop data, so ideally you only need to match the drop mils to whatever wind mils you've collected. The drop mils are actual, but the wind mils are based on calculation.

Hornady 26335 140gr BTHP Match
Ballistic Coefficient (G1) = .580
Sectional Density = .287
Bullet Length = 1.325"
Barrel Twist = 1:8"
Sight Height = 1.85"

Zero Data: 4660 FT @ 60 F 2750 ft/s
Load Data: 4220 FT @ 63-70F
Yards | Elev. | 3-wind | 5-wind | 7-wind | 10-wind
220 = 0.5 mil | 0.1 mil | 0.2 mil | 0.2 mil | 0.3 mil
420 = 1.8 mil | 0.2 mil | 0.3 mil | 0.5 mil | 0.7 mil
550 = 2.7 mil | 0.3 mil | 0.4 mil | 0.6 mil | 0.9 mil
665 = 3.8 mil | 0.4 mil | 0.6 mil | 0.8 mil | 1.1 mil
860 = 5.6 mil | 0.5 mil | 0.8 mil | 1.1 mil | 1.5 mil

[Das Capitolin]

You are doing it wrong.
Go shoot.
Note the wind speed with a handheld meter.
Note the wind conditions between your firing point and target and compare them to your firing point.
Fire at the target.
Note the amount of wind drift.
Learn to work from a 10mph 90 degree wind as "full value" and how to value angles and speeds to the standard 10mph "full value" figure.
No need to worry about 3mph or 5mph or 7mph drift as those are just "pieces of the pie".
Only the full pie and the "value" of the wind matters.

Do that enough and you will just KNOW how much wind to hold in specific conditions.
Wind changes so fast that by the time you look at your chart and figure out how much wind you need to hold or dial, it has already changed.

Mirage is your best instant indicator of the total wind conditions.
Learn to read mirage.
Learn how to hold-off based on mirage.

A bit presumptuous, aren't we? I already know how to read wind, vapor movement, and boil, thank you very much. As I stated in my post, I do not get the opportunity to record wind readings during a match, and I also don't have the opportunity to re-create the match environment elsewhere. All I'm trying to do is see if the calculated wind drift is close to values others have collected for similar drop. If you're not capable of sharing, or helping, then don't respond.

[ar15barrels]

All I'm trying to do is see if the calculated wind drift is close to values others have collected for similar drop.

Drop has little to do with wind drift.
Use your velocity, BC and your atmospheric conditions, calculate it with a program and run with it.
After firing in actual conditions, adjust your hold as needed.

[thegiff]

A bit presumptuous, aren't we? I already know how to read wind, vapor movement, and boil, thank you very much. As I stated in my post, I do not get the opportunity to record wind readings during a match, and I also don't have the opportunity to re-create the match environment elsewhere. All I'm trying to do is see if the calculated wind drift is close to values others have collected for similar drop. If you're not capable of sharing, or helping, then don't respond.

You say you can read wind, vapor movement and boil, that means you know what the wind speed is/was. So I think you should then take better notes during the match or practice as to what you saw and your actual drift. It would only take a few seconds to record 5mph 1/2 value right. 5 .5R for instance after a relay. If you can't do this, then up your game until you can. Notes like this are important to improving I've found.

If you are asking the question does calculated drift correspond to measured drift? Then: I'd say that while I'm shooting a different caliber, the calcs are accurate IF and this is a big IF, IF the wind is constant. I was able to see this only a couple of times in the last year, shooting every other weekend. Shot at 1000yd for the first time a few months ago, and had a steady and even crosswind, and the drift corresponded to the calc and measured speed. 18" or so... Then the wind switch direction, and moved to the other side of the bull entirely. Most of the time the wind changes too fast, or is in two directions or more across the range, and it is all educated guess for the first shot and corrections if you can see your hits for following shots.

But, you seem to be asking does drop/drift correspond?
Yes, but they are independent, hence the previous answer given, what difference does it make? They are independent. This means one does not correspond to the other. There is a dependency related to BC, better BC = lower drop and lower drift, but since drop and drift are calculated independently, we are back to independent relations.
Keep in mind wind can be vertical, then you get gravity drop + horizontal wind drift + vertical wind drift. Not common in my limited experience, but I've seen it in a canyon where a headwind was coming up a berm and you shoot over the berm. Nearly everone missed high due to the landscape affecting the vertical wind.

[Das Capitolin]

You say you can read wind, vapor movement and boil, that means you know what the wind speed is/was. So I think you should then take better notes during the match or practice as to what you saw and your actual drift. It would only take a few seconds to record 5mph 1/2 value right. 5 .5R for instance after a relay. If you can't do this, then up your game until you can. Notes like this are important to improving I've found.

I think you should show up to one of our tactical varmint matches, and show me how it's done. It sounds like you're so good that recording wind readings and settings won't be a problem while shooting at five spotter-selected targets at five distances between 220-865 yards in under three minutes. It would be simple to record wind during the brief sight-in period, but there's rarely any wind at 8AM.

Your criticism of my ability aside, the rest of your response was what I was referring to in my post.

[thegiff]

Quoting myself below, this is what I do and why... Educated guess, then correct following shots.

Most of the time the wind changes too fast, or is in two directions or more across the range, and it is all educated guess for the first shot and corrections if you can see your hits for following shots.

I think you should show up to one of our tactical varmint matches, and show me how it's done. It sounds like you're so good that recording wind readings and settings won't be a problem while shooting at five spotter-selected targets at five distances between 220-865 yards in under three minutes. It would be simple to record wind during the brief sight-in period, but there's rarely any wind at 8AM.

Internet jabbing aside, truth is I miss wind calls more often than get them right, one reason you mentioned above, the wind is different throughout the day. But I do take some notes after the stage, not during. Then try to correlate what I measured, what I saw, and what I did for corrections to try and get better for the next time out. It helps to build up a database for a specific range. You can only measure where you are after all. If you shoot a lot at any one range, you can learn the conditions for that range and beat outsiders or those who don't know that range and its microclimate.

Anyway, the calcs are dead-on based on the assumption that the wind is constant and known. I've been able to correlate this twice with hard dope. But the reality is that wind is not constant, and building up the correlation between measured wind and impacts is not easy due to this normally false assumption.

[dskit]

To answer the question in a less than roundabout way -

My rule of thumb on my 6.5 Creedmore is .1 mil of windage per 1 mph of wind at 600 yards - so your numbers match that dead on - I would imagine the others would track as well.

To address the other blather noted - you can never be 100% sure of what the wind is doing l in terms of a single MPH/direction number. You can find out what MPH number/ direction happens to work in that particular condition. Hopefully your estimate will get you to hit the target, and you build the observed changes from there. That's how I do it.

[Das Capitolin]

To answer the question in a less than roundabout way -

My rule of thumb on my 6.5 Creedmore is .1 mil of windage per 1 mph of wind at 600 yards - so your numbers match that dead on - I would imagine the others would track as well.

To address the other blather noted - you can never be 100% sure of what the wind is doing l in terms of a single MPH/direction number. You can find out what MPH number/ direction happens to work in that particular condition. Hopefully your estimate will get you to hit the target, and you build the observed changes from there. That's how I do it.

Thank you for the confirmation. These are just calculated numbers so I can have a starting point, since this is a new rifle with no prior data on the bullet. Obviously conditions will change, but it's good to have a point of reference.