09-06-2020, 02:19 AM
Was the ammo outside between morning and afternoon or in the sun? Or in a hot car? It's the temp of the ammo - not the ambient temp that matters. But yes, I have found it to be extremely temp sensitive. When I lived in the mountains of CO, I used 30.8 grains at 2560 out of a 22". Ammo was probably stored in the mid sixties, kept in the shade at the range and the ambient temp never got much above 90. I'm in Phoenix now, keep my place at 79 and 30.4 grains gives me 2600 when it's 95-100 out. The old 30.8 grain load gave me around 2650 here with significant velocity variation and as you could guess, light ejector marks. These numbers are from different 8 pound jugs and I would attribute some of the difference to differing lots. The lot I'm using now is definitely faster.
Let's go Brandon!