I think a better method to determing wall thickness would be to get several cases of different brands...
Weigh the case and then fill it with water--weigh again...
Subtract empty case weight from case + water weight and that will tell you the internal volume of water--more water, thiner case wall...
All cases will need to be trimmed to the exact same length...
But, I am a bit uncertain as to what the entire purpose of this process might be?...
Still...
Good-luck...BCB