Given a choice, with a thermal chamber at the range. Use the chamber to force the rounds to the right temp, wait for them to stabilize, and fire with a chrono. A small freezer and a thermometer isn't a bad alternative.
With respect to temp testing, I will say that lots of people have done it, and no one gets the same results as anyone else. However, I've seen enough data to become convinced that the ADI/Hodgdon series with Varget, H3450 and Retumbo, plus the Alliant RL-23/RL-16/ARCOMP series are the most temp stable powders available.
The particulars of the load used for testing seem to matter a lot, and I suspect that's why no one's data agrees. As far as I can tell, it boils down to loads being on a velocity node or not. If they're on a node, everything is more stable. If they're on an anti-node, everything is worse. When the charge weights are chosen without respect to a velocity ladder, the results are all over the place. Hotter primers also reduce temp sensitivity. I use Federal 215s on everything for that reason - they're the second highest brisance large primer you can get behind 215 Match and I've had a hard time finding 215 Match reliably.
Last edited by Llama_Bob; 04/16/19.
