Depending on the lot of brass, sometimes there is weight correlation, sometimes none.
The only way to know this much is through actual testing and measurement of both weights and capacities.
If you're going to do that, then you might as well just plan to measure actual capacities and remove any question about it.
But what is sought here is not actually about static weight, nor static capacity.
Instead, and ideally, our cases would match in dynamic expansive energy. This is the energy consumed from peak pressure to expand case walls through clearances and against chamber walls. The influence of this potential variance is complete by then.
Potential expansive energy goes beyond what we can directly measure, but we can indirectly measure & match it.
The energy to put case walls against chamber walls is tied to case diameter/area, loaded clearances, and tensile forces required throughout every expansion. It is intended to set the first two through sizing, but tensile forces are tied to brass hardness.
Well, so is spring back.
There is no useful information regarding either weight or capacity with new brass (in same lot). It was formed approximately and will never be in final form until we put it there with our best die (our chamber). That needs to happen before beginning with this matter.
You can have static capacities all over the place with same weight cases. Pull a weight matching case, smash it with a hammer, and now you have a case matching in weight that has zero capacity. Right? Match new cases by capacity, and some weigh differently with different wall thicknesses and web height/tapers. This affects tensile strength, affecting case dynamics (it's character).
In contrast, you can dip anneal cases, fire form them 3 times to stable with no more than neck sizing.
These cases should be fully formed now and sprung back from chamber walls given their individual character.
This is a good condition to measure H20 capacities.
For those cases matching in H20 capacity, after going through this process, you can be sure they're expanding and springing back with similar energy.
I have fully completed this with several cartridges now, studied the information along the way, and considered all potentials for a credible shortcut. There is only one potential shortcut: Once cases are stable as managed with your sizing plan, and with a well developed load, when you get a flyer -toss the case. Sayonara Marxist brass..
On the flip side, there is the possibility that your load doesn't care about this energy variance. That it appreciates any rough amount of peak pressure attenuation over a certain amount. Diminished returns often correlate with diminished variance of results.
So cases matched, and then Fl sized to never again match, can be just fine.
Back to tossing flyer cases!
