OK, I installed the higher, +3 sight, rather than the +2.5. I thought better too high, than not high enough, I could always file down the front.
With the rear sight set at the first/shorter front sight (bottomed out), I was now shooting approx 18"-20" low, rather than the initial 7" high. However, as the rear sight was sitting as low as it could go, I had lots of room to come up. I was not/am not, concerned about using the rear sight for tracking out to 1000m, so I simply moved the rear sight ladder until it came close (see photo below). I then used the sight "wheel" to fine tune. Low and behold 3 groups later, it's point of aim, point of impact at 100. I've got more than enough room to move back as far as I want to shoot with an iron sight, and come ups. So I'm going to leave it.
As you can see the ladder appears close to the 425ish setting, and basically puts the rear sight in the middle of the "up" position.
The "wheel" is just off the bottom, as the dot before the 3. So there too is lots of come ups left. The bottom is the line to the right of the dot.
Hope this makes sense. I've still got the +2.5 and that probably would have been a better choice and not so low, but now that this +3 is on, I'm going to leave it.
Oh ya, it was a 5 shot group at 2.25". The last shot was just press and hope, as it was -friggin cold here today, so after the 4th shot, the mirage was wild.
140 Hornaday A max. 41.5 H4350