how temp sensitive is powder?

[billm67]

I have been loading shells for many years and I have shot highpower a few years. I have had many rifles that I could get one hole groups out of without too much diffuclty. I am working with a Remington SPS Varmint action in 308. It is in B&C medalist tactical stock (with aluminum bedding block and free floated barrel) and has a rifle basix erv-3 trigger (set at about 10 ounces). It wears a bushnell 6-24 power scope on weaver rings attached to an EGW picatinny rail base. I have loaded 168 gr Hornady match HP's with IMR 4350, AA2520 and Varget. Shooting from a bipod with a rear bag my groups with 4350 were 1.5 inches to 2.0 inches at 100 yards. The AA2520 groups were a little better in that they were 1.0-1.5 inches. The Varget groups showed the most promise in that I had one group that was .750 and the second was .920 (all of the groups were five shots). I am not as thrilled with these groups sizes as I am expecting that this rifle should shoot a little better than what I am seeing.

All of these groups were shot in 38 degree weather with next to no wind. My buddy believes that the issue was that in 38 degree weather, the consistency of the powder is not near as good as it is in 70-80 degree weather. I guess I can believe that, but does anyone else have any thoughts on the idea that the powder is temperature sensitive? I have built three of these rifles identical in the past few years and the previous three have all been outstanding shooters. I am wondering if there really is something to the temperature argument or is I just need to keep working on the load development/rifle tuning. My next step is to have a new crown cut on the barrel, as the crown is the factory crown.

Thanks

Bill

[Pa. Patriot]

Answer: Depends on the powder.

IIRC, Varget is advertised as having low temp sensitivity. I've never tested it myself.