Tom,
A couple years ago I did an article for HANDLOADER on "Beating the Rimfire Shortage," on considerable experimentation with various rounds to duplicate rimfire performance. I did buy a Lyman mold that with typical wheelweights throws a 43.5-grain roundnose, but the most accurate load in the .223 was the 40-grain Speer Spire Point and 16.0 grains of one of your old favorites, IMR4895. (I always have a large supply of IMR4895 n hand as well.) Muzzle velocity in a 22" barrel is just under 1600. 6.0 Trail Boss with the 45 Remington RN shot very well too, at around 1800 fps.
Thanks JB...I'll be writing that one down!