My 243 shoots Hornady 75 gr hp best of what I've tried,,the 58 gr vmax is good too....got about 200 rounds through it now with some of that being HSM 75 gr vmax from Cabelas and I'll settle on the Hornady factory stuff.
Now with my 223,,just got it,,not a Ultra though,,stainless synthetic,,nice gun and only shot 10 rounds so far but I think its gonna be a shooter as most fellows here find out. I went out this afternoon with only shooting sticks for a rest for a quick sight in,,using 45 gr hp Win white box ammo the first 4 shots at close range grouped within 2 inches......can't wait to get it on the bench.