Browning guy; I am no expert and this is anecqdotal at best. But I find that flat base bullets, even down to including 22lr, work great out to 100 yds, then after that, they open up too much. It is as if, no matter what size bullet you are using, and I know I am not describing the mathematics here correctly, that somehow , the atmosphere inside the 1st 100 yds, is guessing at how to grab onto that bullet, and by the time it reaches 100 yds, and after , it figures how to grab onto that flat base a bit; but not evenly of course, it grabs one side, and then another, as it goes downrange.