I used the Winchester Supreme cartridge with the 180 gr. "fail safe" slug in last week's Elk hunt in Wyoming.

From using it from the bench beforehand, I found these loads shot constistently 1" groupings at 100+ yds from my Tikka T3 .300 WM.

From the experience using it on an Elk it seemed to stagger the adult cow I shot at 100 yds the first round just behind the shoulder, so she wasn't going anywhere. The second round through the chest put her down quickly.

That's my experience.