Most specifically regarding the .308 Winchester, well to start. You see I have cases which vary in weight/volume and of course brand as well it is suspected from 153 grains to 181 grains, So assuming a node is found at a particular charge or velocity (barrel time Does in reality the weight/volume have a subtle affect on the burning rate of the powder charge? If so I am thinking that there is also a node of sorts for a particular powder as to it's most consistent burn rate.

Flog away as I am curious as to what others might postulate regarding this miniscule (?) effect.