Try Hodgdon Varget, and you may also want to try Winchester 748, they are moderate burn rate rifle powders that seem to work well in .223.
Varget may be lower flash in short barrels,and it gives excellent accuracy.
Some military powders are low flash( meaning thet less of the powder is burning outside of the barrel) with high velocit obtained, you could call Hodgdon, and ask them which powders in the Hodgdon/ IMR line produce a lower flash signature, also call Sierra's tech line they may be able to suggest a lower flash signature powder.
Update I just called Hodgdon, Varget is their recommendation for higher velocity and lower flash in a short 16" barrel. The Speer manual 13 bears this out as well, for 50-69 grain bullets.