Accuracy Question - Temp/Pressure & accuracy
Experts!
Question -
Will my most accurate load at 75F also be my most accurate load at 30F? I know there is a drop in pressure/FPS etc. but will my all out accuracy stay the same for the load at lower FPS/trajectory or will I have to adjust my loads for colder weather for the same accuracy?
270WSM 140GR. Berger VLD - 69GR. Retumbo 3219FPS @ 75F
1/2" 3 round group.
Question -
Will my most accurate load at 75F also be my most accurate load at 30F? I know there is a drop in pressure/FPS etc. but will my all out accuracy stay the same for the load at lower FPS/trajectory or will I have to adjust my loads for colder weather for the same accuracy?
270WSM 140GR. Berger VLD - 69GR. Retumbo 3219FPS @ 75F
1/2" 3 round group.
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Great question.
My guess?
It depends. Lots of testing; your rifle, your load. Eventually you'll get the real answer. For you.
Looking forward to what others have to say and to updates on your own testing.0 -
I don't believe that anybody can give you a factual answer in this matter. It my personal experience that it's much more difficult shooting when it's below freezing, then in pleasant shirtsleeve weather. When your freezing your butt off it's makes it hard to concentrate on your target, over and above how the change in weather affects the powder. 0 -
A factor that can also cause variations in performance is humidity. In particular, if you are loading in a very humid environment, any moisture in the powder will be affected by below freezing temps.
As the previous posts noted, you have to test your loads with your rifle in various conditions in order to see how all the variables affect the out come. Testing is the key to answering your own question.0 -
quote:Originally posted by midnightrunpaintballer
Actually your accuracy happens at a specific velocity that your barrel has decided to like. As temperature changes, so will velocity, and therefore accuracy. I have found that my difference in accuracy between cold and warm days can be corrected by changing a half grain of powder whichever way needed. Ymmv depending on conditions where you are located.
Basically, chrono your loads when it gets cold where you are. If velocity changes and groups open up, add a half grain of powder to get velocity back up to where you know its accurate.
Most people wont notice the difference. Based on the info you've shared, id guess that you, like me, have a higher standard of accuracy than most people.
Rem 700 .223
Pillar bedded boyds stock
lapua brass
Cci br 4 primers
win 748 powder. Load depends on conditions. Dont have my notes with me
berger 55's
.40"s for 5 shots@ 100yds0 -
Apples to apples, about the same. Had a chance to fire under wildly varying conditions when I spent 2 years in Fairbanks. In extreme cold (-60F) chamber pressures as a tad higher-my theory was that your .308 bore was no longer .308 due to temperature contraction. Whether that is correct- don't know. But your best 70 degree load wwould usually be about your best -25 load- accuracy seemed to decline evenly in severe cold.
Depending on temps, expect lower velocities. Colder air is denser, humidity levels usually lower (also contributes to increased density). Winter parachute jumps there in Northern Alaska were a hoot- SLOW descent (relatively speaking)
We did have firearm parts break in very low temps- mainly firing pins (brittle), and lubricated firearms were a real problem.0 -
According to Hodgdon, yes.
Retumbo is an "Extreme" powder not sensitive to temperature.
I use only Extreme Hodgdon powders for rifle. I play with my gun mostly in the off season and I want my loads to shoot the same in the fall/winter months.0
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