Well when I say that you need to work up a load again. You do but I dont start from scratch. If my load is 26gr WC844 from a tested lot.
I may load a few at 24,25 and 26 and run them over the chronograph. Then take the closest to my FPS from the last batch and work up or down until I get it back in the same range.
Basically thats what the military does. When they run out of one batch they mix up a new one. Test the powder to fit the expected load and load all the ammo with that new recipe.
Thank you for the help with switching to WC844, now if I can find some. A lot of places are out of H335 right now.