bullet impact change (weather)
- Thread starter reloaders
- Start date
LongBomber
CGN Regular
- Location
- Fernie, bc
Short answer - Yes. Someone with more experience than me can quantify all the variables.
You may also see group size changes, in the cold you may have to increase your powder charges to maintain the velocity you found your accuracy at. And if you develop your loads in the cold, you may need to reduce the charge in the heat. At longer ranges you should see an increase in bullet drop in the cold, due to reduced velocity and thicker air conditions.
You may also see group size changes, in the cold you may have to increase your powder charges to maintain the velocity you found your accuracy at. And if you develop your loads in the cold, you may need to reduce the charge in the heat. At longer ranges you should see an increase in bullet drop in the cold, due to reduced velocity and thicker air conditions.
- Location
- Niagara Region, Ontario. For now
Did u sight in the gun with a cold bore, waiting for it to cool completely between shots?
If the guns barrel was warm when you sighted it in, and now you are sitting in a treestand for hours in the winter, to the point your barrel is freezing, then yes there will be some difference.
For longer range stuff the cold will also affect some powders differently as well. H335 in my .223 loads was affected quite a bit between 0 - 30 degrees, causing significant changes in accuracy.
If the guns barrel was warm when you sighted it in, and now you are sitting in a treestand for hours in the winter, to the point your barrel is freezing, then yes there will be some difference.
For longer range stuff the cold will also affect some powders differently as well. H335 in my .223 loads was affected quite a bit between 0 - 30 degrees, causing significant changes in accuracy.
An old rule of thumb was 1/4 minute per 10 degrees F at 1000 yards just for the heavy air. That's assumeing no change in velocity or zero; which is a pretty big assumption. Also don't assume that a load won't go sour when the temps drop.
When we were being trained as snipers, we soon found out that with the issue "match" ammo for 7.62 x 51 mm at 800 m we had a drop of around 5 cm (2") at ambient temperature of 10 C compared to that at 32 C at the same elevation. In both cases, the shots recorded were from a hot barrel ( five shots fired within 30 s) and with the ammo kept against the body (under the winter jacket in the winter until loaded one round at a time) to minimize all other variations and determine the effect of air density on the bullet. So, yes, ambient temperature plays a role but we also found out that ammo and barrel temperature had a bigger effect. I hope this gives you some guidance as what to expect.
- Location
- Prince Albert, Sk
I found that playing around with ballistics software will give you a "formulated" guide as to drop with temperature,elevation, barometric pressure, and sometimes humidity.
However it is no test for real world test conditions.
However it is no test for real world test conditions.
We had a one inch drop with rimfire at 100 yards within 5 minutes time. It went from hot to very cool in a matter of seconds, cloud cover, moist cool air blew in at the front of a weather system. The change was significant in bullet impact. We were shooting under 1/2 inch groups before and after so indeed it was the weather not the equipment.
(Walther GX-1 rifle and Eley tennex red box....so yes we were shooting small groups at 100 yards)
Yes temp and weather affect ballistics a lot.
(Walther GX-1 rifle and Eley tennex red box....so yes we were shooting small groups at 100 yards)
Yes temp and weather affect ballistics a lot.
Mystic Precision
CGN Ultra frequent flyer
- Location
- Summerland, BC
The only way to know for sure is test. Besides your load, you also need to confirm the properties of your barrel and stock AND scope.
Test, test and more tests....
As to ambient changing POI, we can easily see 1 min change in elevation during a F class relay which is like 15 mins long. Cloud/sun or moving cold fronts really screw with your elevation. A change in tailwind/headwind can blow you more then that.
Going from summer to fall and all the weather that can bring, you bet there will be a change....
Jerry
Test, test and more tests....
As to ambient changing POI, we can easily see 1 min change in elevation during a F class relay which is like 15 mins long. Cloud/sun or moving cold fronts really screw with your elevation. A change in tailwind/headwind can blow you more then that.
Going from summer to fall and all the weather that can bring, you bet there will be a change....
Jerry
Ballistics software will tell you what air density does. The change in temp will affect muzzle velocity, which software can deal with, and barrel harmonics, which can't be predicted. Temperature may affect your scope.
So some effects are predictable, some have to be tested by actual shooting.
So some effects are predictable, some have to be tested by actual shooting.
Density Altitude will also affect POI.
A Kestrel with this optin will tell you both your Altitude and your Density Altitude as long as you have the correct barometric pressure input.
Just because your elevation (as an example) is 2000 ft it does not always mean your are shooting through air density that you would find at 2000 ft. The Density Altitude might be 1000 ft in the morning and 3000 ft in the afternoon.
There are many more variables than just temp to affect your POI on any given day.
As to temp changing the accuracy of your load that will be dependant on what powder you are using since different powders react differently to temperature change.
My 6BR with Varget uses the same load winter and summer.
A Kestrel with this optin will tell you both your Altitude and your Density Altitude as long as you have the correct barometric pressure input.
Just because your elevation (as an example) is 2000 ft it does not always mean your are shooting through air density that you would find at 2000 ft. The Density Altitude might be 1000 ft in the morning and 3000 ft in the afternoon.
There are many more variables than just temp to affect your POI on any given day.
As to temp changing the accuracy of your load that will be dependant on what powder you are using since different powders react differently to temperature change.
My 6BR with Varget uses the same load winter and summer.
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