It still will not likely match in results.
While most have formed a notion that measuring and matching case H20 capacity is about initial confinement, that is not as useful as you might think. This, because it's a static measure, while results are dynamic.
Some contributing matters include chamber clearance and support, brass alloy and hardness, load density and pressure. These are the things you need to match, and capacity measure can get you there, but here lies the difference: the prerequisite for dynamic capacity is control of all contributing.
A single static measure does not get you there.
So how can you see and know that I'm right about this?
Well, without countering with sizing, you can watch MV change from new brass to fully fire formed.
The new brass has less capacity/tighter confinement for a given load, you should see MV high at first and lowering with each firing on cases, right?
Except,, it's just opposite..
The new cases are expanding more, and with this absorbing some of the pressure peak. It's like a shock absorber to the peak, which is often beneficial because it flattens the peak to plateau.
FL sizing functions to recharge some of the shock absorbing, but at counterproductive costs (like brass hardening, clearance changing, additional capacity variances).
For brutal real matching, you must 1st match every aspect of your cases, then take capacity measure after cases are taken to fully stable -with your sizing plan.
In my experience, you're lucky to match 10% of new brass in every respect, and of that, I've lost ~20% to departures in dynamic capacities (what the cases spring back to from chamber + sizing die). And I'm a tight chamber/minimal sizing dude.
If you're a FL sizing dude, forget the whole mess. You will never reach dynamic capacity matching.
Obviously this is not a disaster. But it is a reason not to lose religion over H20 capacities.
Just don't bother for no good reason.
