I finally took my Buffalo Classic out to the range today and got to shoot it at 600 yards. I have the lowest Lyman front sight that there is.
The Williams FP will allow for a zero out to 600 yards. However, I don't think the standard Remington Green Box 405 grain bullets are consistent enough to sustain groups at that range. I could be wrong, though. There was some confusion reporting my shots.
First, I shot a group at 300 yards. It was about 7".
Then I did some calculations and set my sights to 600 yards, up about 40 clicks from the 300 yard zero. Apparently, my first two rounds hit paper but the spotter in the pit missed them. (I was told later.) So I started adjusting when I shouldn't have and things degraded from there. The good news is that there is enough adjustment on the FP that I bought from HR/NEF to go 600 yards if I want to, and if I have consistent ammo.