Two specifications:

Case water capacity
Case water overflow capacity.

The former is what you describe measuring. It’s limitation is it is only accurate for one bullet seating depth.

Case water overflow capacity is not literally an overflow, but you take a case trimmed to nominal trim length and fill it with water level with the mouth (no meniscus). Any program (like QuickLOAD) that knows the size and shape of the bullet can then subtract the bullet volume that is seated into the case for any seating depth you want to try.

In general, if the round peaks at a pressure in excess of 30,000 psi, you measure the case water overflow capacity of the fired case because that’s the volume the powder will be burning in for most of the way to the pressure peak. If the round peaks below that level, then the case water overflow capacity of the case as-resized gives a better pressure and velocity prediction.

So I’m sold on H20 it provide very accurate load data when you use new brass, change bullets ect.

My buddy was able to run my velocity tell me my current case specs and also let me know how much variation in cases I could get away with before it would effect my scores.p and drop me out of the XRing ect.

At 100 yards it doesn’t mean much but at 1000 I want the tightest vertical I can get so I can concentrate on wind.

We then cronographed my 308 load. Based on his live data he was able to tell me what my case specs where. I went home and confirmed everything he said.

So why is it useful, If you decide to switch bullets, change seating depth, neck length, or even get a batch of new brass, you name it, you will know what charge to use to match your last Cherry load.

Also, you will know what cases need to be removed from the lot. 2 grains of H2O could effect your velocity enought to keep you out of the XRing.

Yes loading a bullet would give accurate measurement but you just turned your case into a hydrolic piston, could blow your plug out , expand a case, rust your tools, it would not be very efficient. A loading program takes bullet specs into consideration.

I do have to laught, the chewing gum just gave me an idea, I just saw my kids silly putty sitting one the table.

This may not be a tool you use often but seems quick and can be used on freshly tumbled brass with primer removed.

Bob: You are correct. However, most of the universal decapping dies have a 0.0625″ or larger diameter decapping pin that will stick in the 0.059″ flashholes of 220 Russian, 6PPC, 6mmBR, 6.5×47 cases etc. — unless you turn down the diameter of the pin. For that reason, we don’t routinely tell people to use a universal decapping die (without qualification). But if one has large flash holes, the procedure you recommend will work fine.

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