checking case capacity

[saum2]

Is plain water the best way to check capacity in different branded brass? Or something else.
Geoff

[Cameron Mc]

Geoff, try metho.

Cam

[ecomeat]

So my "dip em in the cattle water trough" that I did to get case capacities of 3 calibres for Quickload mightn't have been such a good idea after all ?
Does metho dry right out easily without any sort of oily residue ?

[williada]

Whether its water or metho make sure the cases have dried out with no residues. I once loaded meticulously for a two day event even though I thought a couple of days of airing would be sufficient for evaporation of the metho I used, I came to grief. Perhaps cleaning my cases first, then warming the cases to evaporate the metho then maybe tumbling would have removed the oily residue which penetrated my primers. I don't live in a warm climate. I know metho works, and is easier and less messy to use when taking these measurements. I do a sample batch with water these days and just take my time.

[saum2]

Thanks Cam. Metho it is.
cheers
Geoff

[Malcolm Hill]

Geoff
Make sure the cases you want to compare have all been fireformed in the same rifle and then trimmed to the same length. I find using some old ball powder gives better and easier checking of the internal volume than using water which can have air bubbles trapped in the shoulder as well as inconsistent levels at the top of the neck (depending on the water tension). Use whatever to block the flash hole - an old primer seated backwards works for me. Most good quality cases don't have much variation between them lot to lot, but brand to brand can give some surprises.
Regards Malcolm.

[saum2]

Thanks Malcolm,
I'm checking the difference between Norma cases and some Winchester for the 7SAUM. Trying to use a similar load in the Win brass if I can as they weigh quite differently. Just wondering, probably too much time on my hands.
cheers
Geoff

[higginsdj]

Sorry if this is a stupid question but you wiegh the case dry then full, find the difference then that is the capacity for each case - right?

Cheers

David

[Barry Davies]

That is the water capacity of the case and is a direct indication of case volume differences --providing of course there are no air bubbles locked up within the case -- which you have no way of telling.

[ecomeat]

Correct, David.
There seems to be a consensus of opinion (at least in comments online re Quickload) that you should do an average based on at least 5 cases, but 10 or more is better.
Tony

[bsouthernau]

I noted the use of metho as an alternative to water in earlier posts. Most applications call for case capacity in grains of water - how do the two compare?

Barry

[DaveMc]

Metho 'wets" the wall of the case better and thus leaves less air bubbles. Best method is to wet the case with metho once, empty and then fill again. As stated earlier with fireformed cases cut to same length you should get a very accurate measurement if you pay careful attention to the meniscus. In some of the case volume experiments we did with careful scientific measurement we could get metho volumes down to an sd of 0.001mg metho volume. Water was far more erratic and could indeed get air pockets even with careful attention due to the higher surface tension of the water. The meniscus is a little harder to deal with as well. Once again weigh a dry case, pre wet the case (a couple of times with water and a few taps then slowly fill and tap. make sure water is exactly level with top of your case each time. Even with great care and attention I found the repeatability of the water about half the accuracy of the metho but far more tedious.

Another good trick is to seat a lead shot (I think BB (or #2) for large rifle) in the primer flash hole using a standard primer seater applies a great seal. (of course tare the shell with lead seal applied).

also remember when comparing case capacities don't forget to take into account the seating depth where projectile contacts the rifling. If using quickload you can enter case volumes to case mouth and then use seating depth on LHS to correct. If using same chamber and different brass (I assume you mean rem vs norma in 7saum) then it will be close enough o use case mouth comparisons. Just understand the ratio will be (volume case 1 - constant)/(volume case 2 - constant) rather than volume case1/volume case 2. There is a slight difference in percentages.

Specific gravity of metho can be 0.79-0.89 (water is 1). Best way to check is to weigh an accurately measured amount of each you have on stock (should be against distilled water).

[RDavies]

Have you found much correlation between case weight and case volume??

[DaveMc]

Yes

[RDavies]

Yes

Whoa Dave, can you just tone your responses down so us technically inept people can keep up.