Range Report Cold Weather Shooting - Bullet Drop

[FA Duk]

Over the past two weekends I’ve noticed rather extreme bullet drop when shooting below 30 degrees (above 25) with a pressure around 28.5 -29.3 and high humidity - 68-85. Had to bump DOPE up by over 2.5MILS over 900 yards to get on target.

Is there a room of thumb when shooting in cold weather ... ie, below 30, below 15 etc?

 

[Steel head]

Are you figuring in any speed loss from powder sensitivity along with density altitude?

 

[FA Duk]

Are you figuring in any speed loss from powder sensitivity along with density altitude?

no ... shooting Hornady ELD-M and Federal Gold Match factory ammo in 6.5 and 300WM respectfully

 

[Steel head]

no ... shooting Hornady ELD-M and Federal Gold Match factory ammo in 6.5 and 300WM respectfully

You kinda need to map your temp=speed difference or if that latest shooting scenario is repeatable log it in as dope for the next time it occurs.

 

[tnichols]

My 308 lives on a steady diet of FGMM and the 260 a handload over H4350. Typically, I’ll go out and shoot in temps down to -10F. With that being said, I’ve never needed more than a tenth of a mil correction in those situations. Make sure your entering good data into your calc. 2.5 mils is a ton if it’s just a temp thing. Just my .02 I should add that my targets are from 655 yards out to 1K

 

[FA Duk]

My 308 lives on a steady diet of FGMM and the 260 a handload over H4350. Typically, I’ll go out and shoot in temps down to -10F. With that being said, I’ve never needed more than a tenth of a mil correction in those situations. Make sure your entering good data into your calc. 2.5 mils is a ton if it’s just a temp thing. Just my .02 I should add that my targets are from 655 yards out to 1K

thought the same but confirmed. This said we also had light snow falling and shooting over a valley with a cold water river.

I’d be interested to know if your getting your .308 to hold groups at 1000 yds vsjust lobbing them in there. I’ve noticed my rounds tend to fail past 900.

 

[tnichols]

If you confirmed good data entry, and both rifles are exhibiting this tendency, it could very well be temp sensitivity. If just one of the rifles exhibited this, I would suspect scope tracking. As I previously stated, 2.5 mils is a bunch and I've not personally seen that much temp variation with FGMM in the 308 offering.

With a 260 in the stable I rarely take MY 308 out to 1K, especially in the winter months. It's a 20" and with FGMM I'm getting 2533 for an MV. With that MV, it's into the subsonic range at about 950 yards. With today's weather here and my rifle, you looking at 13.2 mils of elevation and you're going to have to call wind within 1 mph as it's a 0.3 of a mil deviation in wind hold.

Sorry that got long winded, but you would probably see a fair amount of vertical dispersion and hit and miss on the wind. So, yes, it would be lobbing.

 

[seansmd]

@Jack Master posted these which show what you are seeing, da based but show the temp changing effects.

 

[FA Duk]

@Jack Master posted these which show what you are seeing, da based but show the temp changing effects.View attachment 7235826

would love to see the data sheet for 140 and 143G ELDM. Where is this coming from?

 

[seansmd]

You create this from your dope on your gun.

You need to go and shoot your gun at know distance and capture all the relevant data on paper. Gun settings, ammo specs, environment, zero range, etc. Then you can go back and true this up with various ballistic programs or apps (most free). Once you have this it is very easy to make DA or temperature charts for your gun and ammo combination.

They are all different.

This is my gun, shot known distances with a solid zero, 3 shot groups on freshly painted steel with waterline. Captured all data on paper, then when home trued MV @ 598y distance(YELLOW), and trued BC @890y (BLUE if needed) on several apps and Kestrel.

Then printed paper for my wrist coach for our club match this past weekend, I knew the morning would be roughly ZERO DA, and in the afternoon up to 1000 DA so I captured only where the DOPE would change to make it easier to see quickly. You could do the same for 20 degree changes in temp at a fixed altitude.

 

[FA Duk]

You create this from your dope on your gun.

You need to go and shoot your gun at know distance and capture all the relevant data on paper. Gun settings, ammo specs, environment, zero range, etc. Then you can go back and true this up with various ballistic programs or apps (most free). Once you have this it is very easy to make DA or temperature charts for your gun and ammo combination.

They are all different.

This is my gun, shot known distances with a solid zero, 3 shot groups on freshly painted steel with waterline. Captured all data on paper, then when home trued MV @ 598y distance(YELLOW), and trued BC @890y (BLUE if needed) on several apps and Kestrel.

View attachment 7235994

Then printed paper for my wrist coach for our club match this past weekend, I knew the morning would be roughly ZERO DA, and in the afternoon up to 1000 DA so I captured only where the DOPE would change to make it easier to see quickly. You could do the same for 20 degree changes in temp at a fixed altitude.

View attachment 7236003

Thx, I’ve got good data on zero, MIL settings for 900, 1000, 1079 & 1202 yards to include Temp, Baro. pressure and humidity ... alas I haven’t invested in a good crono yet and I don’t trust the factory ammo spec. On the box. Been putting this off and I guess I should cry one more time buying equipment as I’m now up to 600rnds between three guns (6.5, 300WM and the .308) each month!

 

[Jack Master]

would love to see the data sheet for 140 and 143G ELDM. Where is this coming from?

I am getting this by playing the Horandy 4DoF app plugging in different environmental conditions.
Here is my info for a 6.5 Creed Hornady 140ELD Match Ammunition (factory Loads)
(data - MV=2650fps - Zero Wind - 50% Humidity (cuz Humidity doesn't matter very much))

Sta. Pressure=28.95 - Temp=90 Deg - (DA = ~3500ft) - Bullet Drop at 900 Yards is 7.45Mil
Sta Pressure=28.95 - Temp=30 Deg - (DA= ~-500ft) - Bullet Drop at 900 is 7.80
There should be about 0.3 to 0.5 Mils of change in your shooting.
To get a 2.5 Mil Change at 900 Yards is about 280fps of Velocity Change.

I'd have to agree, 2.5 mils at 900 yards is a BIG change and my guess, with the limited information we have, is there is something else that changed. Here is a list of things to think about that could change your outcome.

1. Temperature of the gun powder - I don't expect this to change 2.5 mils but if you have an unstable temp powder a larger MV swing can happen
2. Did you change shooting position? Were you prone this summer and now on a bench in the winter? This can change your MV by 20-30fps if you don't manage your recoil correctly. A difference in clothing can also effect this, like a puffy winter coat.
3. Are you having higher winds Left to Right that could cause aerodynamic jumping? (would take a lot of wind to get 2 mils, like 50mph)
4. Did your rifle Zero change? Have you adjusted is recently and why did you adjust it?
5. Is you scope tracking and returning to zero. - is it the same scope??
6. Is this the same Ammunition you used previously? Did you switch brands? Switch Bullets? Switch Ammo/Bullet/Powder Lots

Is there a room of thumb when shooting in cold weather ... ie, below 30, below 15 etc?

Yes there is.
First understand what Density Altitude(DA) is and how it effects you bullet flight path. Temperature is the major contributor to DA changes. Second - there a rule of thumb in the margin of my charts @seansmd posted. (+- 15 Degrees Temp = +- 500ft DA) I take the temp change into effect with the DA calculations. I got most of this information from the late Linden B. (Lindy) Sisk's website. I think he was part of "Rifles Only" in Texas and the HMFIC knew him as well (I think)

Linden B. (Lindy) Sisk

I hope this helps. Keep us posted with more of your results.

P.S. A good Chrono will not fix this issue, this is too big to be just a MV issue (unless its a different ammo or bad Lot of product)

 

[FA Duk]

I am getting this by playing the Horandy 4DoF app plugging in different environmental conditions.
Here is my info for a 6.5 Creed Hornady 140ELD Match Ammunition (factory Loads)
(data - MV=2650fps - Zero Wind - 50% Humidity (cuz Humidity doesn't matter very much))

Sta. Pressure=28.95 - Temp=90 Deg - (DA = ~3500ft) - Bullet Drop at 900 Yards is 7.45Mil
Sta Pressure=28.95 - Temp=30 Deg - (DA= ~-500ft) - Bullet Drop at 900 is 7.80
There should be about 0.3 to 0.5 Mils of change in your shooting.
To get a 2.5 Mil Change at 900 Yards is about 280fps of Velocity Change.

I'd have to agree, 2.5 mils at 900 yards is a BIG change and my guess, with the limited information we have, is there is something else that changed. Here is a list of things to think about that could change your outcome.

1. Temperature of the gun powder - I don't expect this to change 2.5 mils but if you have an unstable temp powder a larger MV swing can happen
2. Did you change shooting position? Were you prone this summer and now on a bench in the winter? This can change your MV by 20-30fps if you don't manage your recoil correctly. A difference in clothing can also effect this, like a puffy winter coat.
3. Are you having higher winds Left to Right that could cause aerodynamic jumping? (would take a lot of wind to get 2 mils, like 50mph)
4. Did your rifle Zero change? Have you adjusted is recently and why did you adjust it?
5. Is you scope tracking and returning to zero. - is it the same scope??
6. Is this the same Ammunition you used previously? Did you switch brands? Switch Bullets? Switch Ammo/Bullet/Powder Lots


Yes there is.
First understand what Density Altitude(DA) is and how it effects you bullet flight path. Temperature is the major contributor to DA changes. Second - there a rule of thumb in the margin of my charts @seansmd posted. (+- 15 Degrees Temp = +- 500ft DA) I take the temp change into effect with the DA calculations. I got most of this information from the late Linden B. (Lindy) Sisk's website. I think he was part of "Rifles Only" in Texas and the HMFIC knew him as well (I think)

Linden B. (Lindy) Sisk

I hope this helps. Keep us posted with more of your results.

P.S. A good Chrono will not fix this issue, this is too big to be just a MV issue (unless its a different ammo or bad Lot of product)

a lot to digest but I believe in data and analytics which you are directing me to gather.

a few more observations:
Position is constant - bench but with heavier jacket

Ammo is constant (and drop is occurring with another shooter using same ammo/gun type (MPA .300WM & MPA 6.5Cred.

2.5MIL drop is for 1202 yds with larger than “normal” at 900, 1000, and 1079 (our fixed targets)

Both weekends We had “wet snow falling” with high humidity. Not really all that cold ... 25 degrees

we are only using manually collected dope using a Kestral Drop ... estimating the wind due to range distance. Haven’t purchased a crono. yet but guess we should.

next outing to range (private) will be in Feb and will continue to gather info.

good thing is that I also gathered data for 600, 700 & 800 for the 6.5 and .308 last weekend. Data data data makes for a better shooter in my book!

 

[tnichols]

a lot to digest but I believe in data and analytics which you are directing me to gather.

a few more observations:
Position is constant - bench but with heavier jacket

Ammo is constant (and drop is occurring with another shooter using same ammo/gun type (MPA .300WM & MPA 6.5Cred.

2.5MIL drop is for 1202 yds with larger than “normal” at 900, 1000, and 1079 (our fixed targets)

Both weekends We had “wet snow falling” with high humidity. Not really all that cold ... 25 degrees

we are only using manually collected dope using a Kestral Drop ... estimating the wind due to range distance. Haven’t purchased a crono. yet but guess we should.

next outing to range (private) will be in Feb and will continue to gather info.

good thing is that I also gathered data for 600, 700 & 800 for the 6.5 and .308 last weekend. Data data data makes for a better shooter in my book!

The information that we’ve been working with changed a bit (2.5 mils at 900 vs 2.5 mils at 1200). Your first post vs your last. But none the less, it’s still off by a fair amount.

I just ran the numbers on my 260 on an 80 degree summer day with a low BP and at 900 yards I need 6.6 mils at 900 and 10.8 mils at 1200. Fast forward to winter with a low temp and high BP, I need 6.9 mils at 900 and 11.6 mils at 1200. So, for easy math, summer vs winter, it is a 0.3 mil difference at 900 and a 0.8 mil difference at 1200.

Not even close to 2.5 mils. Something is amiss.

 

[seansmd]

a lot to digest but I believe in data and analytics which you are directing me to gather.

a few more observations:
Position is constant - bench but with heavier jacket

Ammo is constant (and drop is occurring with another shooter using same ammo/gun type (MPA .300WM & MPA 6.5Cred.

2.5MIL drop is for 1202 yds with larger than “normal” at 900, 1000, and 1079 (our fixed targets)

Both weekends We had “wet snow falling” with high humidity. Not really all that cold ... 25 degrees

we are only using manually collected dope using a Kestral Drop ... estimating the wind due to range distance. Haven’t purchased a crono. yet but guess we should.

next outing to range (private) will be in Feb and will continue to gather info.

good thing is that I also gathered data for 600, 700 & 800 for the 6.5 and .308 last weekend. Data data data makes for a better shooter in my book!

First, since you are not reloading and have actual dope and the ability to shoot at meaningful distances a chronograph will not help you. I only use factory ammo and don't need a chrono, I only use it when my shooting makes me suspect that my rifle ammo combination might have slowed or speed up. Regardless I have to verify dope and calibrate mv at known distance, lying to the ballistic calculators to get there curves to line up, the Chrono is only a starting point.

If you look at Jack's data above for a similar 6.5cm even with a 6000 change in DA the change is half of what you observed.

As @tnichols said above something else is going on that is not supported by the data shared.

 

[Steel head]

An unaccounted for wind?
I shoot across steep valleys often.
Unnoticed wind conditions pop up frequently, fairly calm at shooting position and target position, everyone shooting suddenly loosing a mil+ in elevation is fairly common.
Hence my goal to improve my spotting in 2020.

Some weird snow effect?
I’ve shot long distance in snowing conditions but I was an idiot then and didn’t take notes.

If rifles appear to be normal log all that info down and see if it repeats the next time you shoot in those conditions.
If they do try to find some visual clues in a spotting scope and maybe hike the firing line if possibly observe actual conditions.