Cold Weather Load Development

[Jerry]

Shot my new 6 x 47 Lapua recently to sight in and start barrel breakin. Temp. was 22 degrees. Velocity was 100 F.P.S. less than I get with my other 6 x 47 in normal temperature. Am I wasting my time starting load development in this cold weather??
If the load is tuned for cold weather will it be the "accurate" load at normal temperatures?
This is a light gun for 1k competition.

 

[billmo]

Jerry, I don't think you will find a warm weather accuracy load with those temps. I have been told that for app. every 10 degrees of rise on the thermometer it is the equivalent of adding as much as a grain of powder depending on which powder you are using. I don't know this to be a fact but the testing I have done in winter and summer sure lets me know that the powder needs adjusting. And on some wet and muggy days with temps. not varying that much I can tell a difference in the loads that maybe I had shot on a fair dry day. I'm sure there are some guys here that can get right to the details as to why this happens and explain air density, air temp, humidity and the cause and effect of each. Bill

 

[patchhound]

I think your best bet is to find what speed it wants to shoot and go from there. Take notes on the different vel`s you get with low temps. and compare once it warms up. I`ve been shooting with temps down to -10 and the big problem I got seems to be x-presure, things look better when it gets about 20. I`m not counting on finding a good summer time load till summer...But I think its good to learn how cold affects presure too.

 

[billmo]

I agree patchhound. Bill