I got subsonic with Blue Dot, but then BD disappeared from the market. I suspect other powders of about the same burn rate would work, but haven't tried any in the .223, partly because I found it much easier to produce rimfire-equivalent loads in the .22 Hornet.
My Ruger No. 1B shoots the cast Lyman bullet to the top of the post in the Ballistic Plex reticle at 50 yards when the rifle's 3-9x Burris FFII is set on 6x, and sighted-in an inch high at 100 with full-power varmint loads. The powder charge is around 5 grains of 5744, if I recall correctly, and velocity is around 1100 fps.
