Same 55gr bullet? Sako uses in-house SP for 55gr 223 load and Sierra Blitzking for 55gr 243 load. They're both crappy BC wise, especially the SP. Furthermore, 223 is somewhat toned down since it's marketed primarily as small game not varmint load. Like I said previously, there's no shortcuts and you shouldn't use crappy bullets (if you want to maximize longer range results).
From Sako line-up, dropping to 50gr Blitzking in 223 you get flatter trajectory and, if the energy is relevant to you, 46% more energy at 300 meters. And even in 243 you get about same trajectory, markedly less wind drift, and 32% more energy if you go up to 70gr Blitzking. Not that you need the energy, but less drift is always nice. For a reloader, switching to 55gr bullet with better BC (Nosler Ballistic Tip) is also an option, giving flatter trajectory still.