I would shoot the ladders side by side. Shoot one. Allow the barrel to cool to original temp and shot the second. I run mine through Chrony when I shoot a ladder. I think, my logic here, it learn more. I can see charges windows with some powders that have little change in velocity over a several tenths of powder. I also can see the barrel harmonics. Find a flat spot in velocity tht also is on a vibration node, no/little in vertical with 3 shots, and I then only adjust seating depth and neck tension. Then I choose another bullet or powder and start allow over again. You have to be absolutely certain that the vertical is due to the charge variation and not user error. Other it is all worthless.

Here is a little comparison of powders I play with a few years back.

http://forum.accurateshooter.com/ind...78#msg30936678

I would suggest you find a copy of Rifle Accuracy Facts by Harold Vaughn. Good read. Very technical, but explains the physics behind what matters the ladder test useful.

Luck, Tim