If you have an air space in the case, your primer may be igniting a different surface area of powder between shots. We shoot angles in the mountains a bunch, and have noticed this when shooting downhill. We were hitting high even after compensating for the angle. We figured we were igniting a larger surface area than when we were shooting flat.I know load density and bullet jump has been beaten to death but one issue I cannot resolve completely is how the resulting air space affects burn rate and pressure when a bullet is set against the lands. Or shorter such as SAAMI COAL. The load density is the same but air space can be different which intrigues me. Not sure why but one of those questions you ask yourself eating a Twizzler.
JE Custom once stated the extra oxygen can affect burn rate and that statement has "burned" in my memory for a while and recent loading of the .270TH has me thinking about it again once more. JE also stated bench guys preferred compressed loads for that reason to have consistent burn rates.
Sooo, my far to much time to think mode has me wondering the bullet should be seated at juncture of the powder column of slightly compress instead of trying to seat out against lands. I am shooting the 156HH and I may try some measurements to seat deeper in case and run ladder against previous results of stretching them out to max COAL.
Try this or go back to Twizzlers?
because of this, now we always try to find an accuracy node and powder that doesn’t leave much room in the case.