Fellow shot this one, 600yards - same ctg. a 6BR.

http://bulletin.accurateshooter.com/2018/04/amazing-accuracy-sauter-shoots-0-282-group-at-600-yards/

Bart shot a 6mmBR Ackley Improved (6BRA) wildcat cartridge with an 0.272″ neck. This is basically the 6mmBR Norma with a 40° shoulder. The neck is long like the parent cartridge, not short like a 6mm Dasher. Bart was shooting his own 105 grain, 13 Ogive VLD bullets. He calls this new bullet design “The Hammer” (for good reason). Bart’s Hammer 105s were loaded in Lapua brass with Hodgdon H4895 powder and Wolf primers. Bullet tips were trimmed on a Giraud bullet point trimmer, but not pointed. Bart feels that there is too much potential for damaging bullets during pointing, so he does not point his match bullets. Bart had his LabRadar chrono on the bench during the match. Velocities were 2970-2975 fps with single-digit ES.