We all know when we change components, pressures vary. That’s why every manual differs on the min / max loads they list and the test platform used further adds to the variations. Does anyone know what ONE factor when changing bullets of the same weight raises pressure the most assuming they are used in the same rifle with all other components the same? Say when changing from a 180 gr 30 cal partition to a 180 gr 30 cal GameKing in your 300 win mag is lubricity (sp?) the big factor? How about bearing surface? Core hardness?

Is there one factor that when we see it, a flag should go up to be alert for pressure signs, or does the main characteristic that raises pressure change from bullet to bullet?

Bearing surface and manufacture tolerances

Bearing surface & material hardness (ie, monometal). In my .280, 160gr NP give higher vel. than the 160grSpeer I use for practice, about 40fps. Higher vel. usually means higher pressure, all things being relatively equal.