As John said Tac and Big Game are very temp consistant because they are ball powders made first for military use in 7,62x51Nato and other rifle cartriges like 5,56x45Nato with heavy bullet (Tac). They are made in Belgium in Poudrerie de Clermont a plant who belong to the French SNPE and they use a modified Olin brevet. The plant was put at work during the cold war. They even make one very slow ball, slower than Magnum for use in 338Lap and .50Bmg.
The only differences between cilivian and military powders is a conservation product that allows 50years stocking in military wharehouses. May be today this thing is no more real because of the quantities of ammo burn in wars for ten years....
RL15 is from Swedish Bofors company (have good ties with SNPE and Vitahvuori and works together in powders and explosives business).Some batches are used for US military ammo in 5,56x45, not same name but same powders. It seem to be a bit less temp variation resistant, but nothing to brag about.
All the best
Dom
