I am showing my ignorance here but am I correct in understanding the above as claiming that oil on your cartridge case increases the pressure of the load? This seems counter intuitive. If the powder and projectile is unchanged how is the pressure increased? Is it because the oil reduces chamber size some tiny bit, or because the brass fails to grip the chamber walls and so puts more pressure on the bolt face? Have I missed the point entirely?

Am I increasing my load pressure by 30% by leaving case lube on my cartridge cases?