What were the differences on the chronograph?

I use a chronograph on most bench trips and have seen the biggest variations in the Reloader powders in both temperature and different lots. I still shoot it frequently in some cartridges, but not in situations where there is likely to be a significant temperature swing. I use RL 15 quite a bit in the larger cartridges (.375 H&H, etc.) and find it to be very good.

The cartridges on ice thing has never worked out well for me. I do keep ammunition in a small cooler (no ice) to keep it from getting hot before shooting, but when the rifle gets hot in summer nothing seems to help enough to make a big difference. I have seen guys put ice packs on their barrels, but when it is that hot I pack up and shoot another day.

H1000 for my 7mm mag. no problem with temp.