Surplus powder varies from lot to lot. Shooting 62gr M855 surplus bullets I've used 3 different lots of 844. 1st lot was surplus pulldown, 2nd described as virgin never loaded, and the 3rd was NEW never loaded.
The surplus pulldown was fastest, the NEW lot was next and the Virgin was slowest. With 24.4 grains I got 2879, 2953, and 3001fps. 25 grains got a little over 3000 with 1 lot, and 3100 with the pulldown, and only 2925 with the slow lot. Velocity numbers approximate.
So not knowing the speed of your lot of WC844 I'd suggest starting at 24 grains and working up to 25 grains which is often stated as the load for 62 fmj. Going over 25 grains watch carefully for pressure signs and expecting 3100 fps approximately in a 20" AR maximum. Used WCC, RP, and LC01 cases with RP 7 1/2 primers and oal at 2.260".
26 grains is too much for a starting load and may be too much for a max load with your powder. Start lower and work up!
If I recommended a good load it'd be 24.8 -25 grains.