I haven't tried their .223 ammo but I can tell you their 7,5x55 ammo for the IG11/K31 is unbelievable.
I was at an open sight (no scopes allowed) shooting in 2000 with the Swiss Rifle Club - Toronto. I was invited with my M96 Swedish Mauser in 6,5x55 and they had their IG11s and Kar31s in 7,5x55. One guy, Bruno, in his mid sixties was punching 10s and "mouches" (2 inch diam) at 300 m (that's 978 ft) routinely. That's less than 2/3 moa! I saw it, I was the one reading his targets up front the targets (Hamilton Canadian Army range).
After that, I went on a search for a Swiss Schmidt-Rubin, which were very rare back then. They are abundant since about a year and cheap for their condition. I got both an IG11 and a K31, mint, for 150$ a piece (the Swiss guy was moving to Dubai and did not want the export troubles). With the kind of accuracy with the RUAG militia surplus (0,75$ per rd), I don't bother to reload the 7,5x55, although I did buy the Lee dies and surplus Boxer brass.
Got a Colt HBAR (1/9 twist) on route. If I can get my hands on surplus RUAG .223, you bet I,m going to try it. Will post results. Regards,