Not sure how it performs out of a barrel shorter than 20". BTW, WC844 is listed by Wideners as performing similarly to H335 (though there a about 5 powders in that range that all perform almost identically in the .223). H335 is very similar to 748 or Ball(C)2, but a little faster so usually a grain or so less. Since 27 grs of 748 flattens primers pretty good,I wouldn't go too much hotter with the WC844. Just keep raising the charge weights by .1 grain and see where you're comfortable with the primer flattening. Ask on
http://www.ar15.com 's reloading forum if you don't get anymore info here.