Thread: Case weight variation powder capacity and significants on the target

If brass / case manufacturers used a standard mix across the board there may be some validity to case weight variations, but as said extractor grooves are even different, the only way to see a difference in capacity is measure cases internal volume, with a fluid that fills every part of the combustion chamber ( for that is what it is). using powder has an inherant issue in that the grains will never stack the same. Shooting at short distances will show hardly any difference its when you get past 600 yds and further you see the difference in case volume showing up as erratic velocities which at distance will show as vertical dispersion.
I suspect but have never tested if you took a Winchester case and an ADI case. That had been fired in the same rifle several times and had completely achieved their true internal volume. Then prepared them with the same charge and primer and projectile and then fired them over a chronograph or printed them on paper at distance, you would then see the difference.

My calculations using a band of 2 grains differnce in each cases capacity shows the smaller capacity case would have a higher pressure and higher velocity.
Using a .308 as my base test pressure goes from 54290 to 59600 thats over 5000 psi!! and the velocity change is a mere 40 fps so would not proove much at 100 yds but at 1000 is ? (didnt get there in calculus).

Any ways thats the difference i dont want... the extra pressure. And yes Micky I am talking about hotrod loads.
For example if I have worked up my loads in Winchester cases and then an ADI case gets in the mix now know I could expect to bump pressure up by 5000 psi, with no other variables altered.