Powder Charge - Cold to Warm Ambient Temps

[ARXV]

I'm working up loads on a .308 with 175gr. Berger LRHPBTs and IMR 4320 that it seems to be good for accuracy. Most shooting will be 600 yd FT/R with some long range in a less-serious fashion. Shooting at 44 degrees F, I have a node that goes from 44.0 to 44.4 grains with no pressure signs. I don't know the velocity at this point (no chrono access) and will probably shoot the 44.2 gr. load. What should I expect to happen as the temps go up this summer? Above at 44.6 grains, the groups spread out pretty dramatically (like .3 moa to nearly 1 moa).

 

[ARXV]

I guess a few more questions would be: Is such a big difference in grouping normal at a .2 grain change? Am I setting myself up for failure by choosing a load in cold weather? Am I worrying too much about it from reading on here about temperature sensitivity?

 

[padom]

Check out the below link to see how much your velocity changes when the temperature changes.

https://www.hodgdon.com/smokeless/extreme/page2.php

You will see between 0-150 degrees H4350 only has a 4fps velocity change. Its very stable across a broad range of temperatures.