I was told that if reloading Lake City brass that you need to reduce your load by 1 grain. Is this true? If so, is one grain enough when reloading .308? Is this because the case wall of the Lake City brass is thicker than say Winchester brass? Thanks!
The case walls on military brass is thicker than commercial brass, therefore decreasing the usable volume inside the case. The same amound of powder in a smaller case will generate more pressure.
Reducing the amount of powder by a grain is not really neccesary, unless you are already at or near the max load. If you are near a max, or anywhere close, it is good to reduce your load for any changes, be it a change in cases, primers or whatever. Just to be safe. A hot load in a standard Win. or Rem. case may be over pressure in a military case.
It would be important, when loading at "close to max," to know the signs of overpressure. I know a little about this, but I am sure there are others with much more experience than me who would elaborate on this subject.