Just wondering if you have shot 55 grain bullets in the past in this rifle? How was the accuracy? How bad are your groups?
Did you start out at 27.2 grains? What brass are you using commercial or mil serp? Are you using mixed brass or sorted brass? What twist barrel do you have?
Here is the load data listed for CFE223 with a 55 grain bullethttp://data.hodgdon.com/cartridge_load.asp
At 27.2 you are on the high end and I would hope that you didn't start there especially if you are using mil serp brass. I am not saying that you are at an unsafe level. But I haven't found the best accuracy when loading to the max in any of my Ar's. With that said I will say I have not used CFE223, but have not heard any bad things about it. Personally I would back your load off to somewhere around 25.0 and work up in 1/2 grain increments to see where you get the best accuracy.
I have found that load data for 223 is very broad depending on the bullet that is used. I personally like a boat tail bullet better myself. Have you tried H335 or Varget? I have been using Varget and have great results with it. H335 proved just as well as Varget but I use Varget in my 308 so its easier to buy 1 powder for both.