I have a 243 Catbird (6mm-06 improved) The rifle is built on a Stolle Kodiak receiver with a Kreiger 1-7.5 twist 29" rem Sendero contour. This rifle shoots 107 SMK and 105 Berger Hybrid Tgts boringly into .2-.3 tenth 5 shot groups at 3480 FPS. I tried some matrix 117 in it and it literally sprayed a 12-15" 5 shot group at 400 yds (the 105 Bergers just shot a 1.3" group at the same distance) The load was retumbo (same powder I use for 105-107 bullets) seated to touch lands and a MV of 3300 fps. The bullets entered the target straight but all over. Is it possible the 1-7.5 at an elevation of 600ft and 3300 fps is not stabilizing these bullets? Any other ideas, I am baffled.