Re: 7mm rem mag ladder test?
For 7mm Mag, I work up from min to max in .5gr increments with R22. I pick a COL that suits the load's purpose and keep with it.
I had to extrapolate R25 load for 168gr SMK. I maxed out at 68.5gr which was 1/2 way between the 160gr max load and 175gr max loads I had R25 data on. I was 200-300 fps below my expected velocity and accuracy was the worse of any of my 7mm loads. The 68.5gr load was the most accurate of this combination, but since the accuracy was bad, I've decided to go back to R22. The felt recoil of the R25 loads were much heavier than other loads.
I use LR primers for most of my 7mm mag loads.
For one load, I am below min on most load data but the load was very accurate. 50gr IMR 4064 and 120gr Nosler BT. I got the load data from Lee book. It was well below other load data.
Aside: for .223, I go up in .3gr increments. But there is about 2-3gr difference between min and max in most of my load data. It is softer shooting than 7mm mag.