This summer, I worked up some nice loads for my 300 BO (supersonic 18in carbine gas). The loads were both jacketed and cast using H110 powder. At 100 yards from the bench, my jacketed bullets would cut each other and the cast loads would give me 3/4 to 1 inch groups.
Fast forward to today. It was 33 when I was at the range and the gun and ammo sat in the cold all night. The cast bullets were giving me 2 inch loads and the jacketed opened up to 1 inch or so.
I never thought of H110 as a temperature sensitive powder but it sure is. I proved it out by heating the ammo with hand warmers and running a fast 10 rounds to heat up the barrel. If I did this and shot single rounds still warm, the groups shrank to close to where they should be. If I loaded up a 20 round mag, you could see the groups spread as the lower ammo in the mag started to cool off.
Well, I guess it is time to work up some LiL Gun loads for the winter and save the H110 loads for the summer.
Fast forward to today. It was 33 when I was at the range and the gun and ammo sat in the cold all night. The cast bullets were giving me 2 inch loads and the jacketed opened up to 1 inch or so.
I never thought of H110 as a temperature sensitive powder but it sure is. I proved it out by heating the ammo with hand warmers and running a fast 10 rounds to heat up the barrel. If I did this and shot single rounds still warm, the groups shrank to close to where they should be. If I loaded up a 20 round mag, you could see the groups spread as the lower ammo in the mag started to cool off.
Well, I guess it is time to work up some LiL Gun loads for the winter and save the H110 loads for the summer.
