Definitely you want to work up a load for each lot of WC844 or WC846 poweder you obtain. I have used both, also the T versions which are definitely hotter for ignition of tracer bullets. Start low and work up a load for each lot of powder you get. Did I mention start low and work up a load for each lot of powder?
This is generally military surplus powder and it is bulk grade powder, NOT cannister grade powder where you can simply use your data from the last can you bought. When the military manufactures powder in a large lot, they adjust each lot of powder to get the burning characteristics they want, rather than trying to make each batch of powder exactly like the last batch. Therefore it is imperative that you start over with each different batch and determine the burning rate and load.
You may be surprised how much variance there can be between lots.
Remember, BE SAFE and careful. Kabooms are bad karma.