Winchester and Ultramax are the two brands that work well in my Ultra .223. I stick with the 55gr or lighter bullets.
I also reload using all Winchester componets, with a Speer bullet. Hodgdon gives the factory duplication load in their magazine size manual. 55gr Speer SP bullet, 26.3gr Winchester 748 powder, Winchester case, Winchester SR primer, giving 3150fps. For 50gr Speer SP bullet, it's 26gr of 748 powder, same case and primer, giving 3200fps. My H&R Ultra, my TCR, and my mini-14s all use these loads.