.223Rem in both a TikkaT3 Lite (sporter barrel) and Savage FP10 (heavy barrel).
Strange but both chambers are the same size so the brass is interchangeable.
19.6 gn IMR 4198 and 55gn bullets
Both shoot sub 0.3"
In a pinch it will also fuel my 22-250's.
Ever tried it with heavy bullets.