Yep, Accuratereloading forums under 'Big Bores' pg 1.
I was looking at an Anglo "ball & shot" 12br and that 300yrd folded leaf......and those 750gr "mushroom-shaped" projectiles. Some of those yardages in that folded rack are just for show, right? I shot some darn good groups from 300m with express sighs, but that was using ZKK 602 300WinMag with Winchester 'Supreme' 190gr Silvertip BTs.