Iv'e been using Benchmark in the 223 and 22-250 for some time now. Like it well enough that I buy 8 lb jugs of it. Gives great velocity in my 22-250 as well as accuracy. In my 22-250 I've been using 36.6 gr under a 40 gr ballistic tip and have been getting 4065 fps, have used that load at 400+ on pdogs. 35 gr of it under 50 rem sp run out at 3800 fps.
In the 223 26.5 gr under a 52 HPBT MK Sierra will run 3450 fps out of my cooper and will stuff them in one ragged hole consistently.
Great powder, clean burning, doesn't seem to be primer sensitive like some other powders are.