You did not say, but I assume they are lead with no jacket. Are they copper plated? If they are a lead alloy with no copper plating or gas check, I would not use them in a 223, I would use them in a loaded down 22 Hornet or not at all. If they are copper plated you can push them into the 2000 fps range. Blue Dot loads for the 223 come to mind for loading down. If they are jacketed, depending on jacket thickness, can go 3800 fps+. Do a search on the 'net for Blue Dot loads in a 223. There has been some experimenting with them, with good results in some cases.
Good Luck and Good Shooting