Testing Case Volumes?

[Dynamic1]

I would appreciate some clarification with regard to testing the volume of cases as one means of sorting.

When do you test the case? If you test before cleaning, when the expended primer is in place, you might expect variation due to carbon build up and before the case has been re-sized. If you test after cleaning, the case must still be re-sized.

It seems to make most sense to measure volume after the case has been re-sized, however, I think you would need to insert a new primer in order for the case to hold water or alcohol. However, is there not a possibility that the fluid might react with the primer propellant and alter the consistency of ignition between each primer and, therefore, affect the accuracy each loaded cartridge?

 

[Dynamic1]

Thanks for the reply.

I thought testing cases for volume was done with a fluid (i.e. water or isopropyl alcohol)?

 

[1shot]

I either test a batch of unfired cases, or deprimed brass after it comes out of the tumbler after a full prep. Using the SS pin method, the brass gets pretty darn clean. Either way I take a small dab of dental impression wax and press into the primer pocket, it doesn't need to be flush, because you are going to re-use it. I then weigh that piece of brass empty, then again when it's filled with H2O. Record the weight differance and empty the case. A dental pick or tooth pick will remove the wax plug easily and you are off to your next case.
I hope this helps,
Lloyd

 

[jlow]

1shot, one concern I have for the use of dental impression wax is unless you can insert the exact amount of this material into the primer pocket and primer hole, the variance will translate directly into variance in case volume. When I did this in the past, I used spent primers that came out of pistol cases (with primers still in them) that I had cleaned with SS media and those primers were pretty clean.

 

[amlevin]

If I'm going to sort my water capacity I just use the fired cases with expended primer in place. I feel that any carbon on the inside of the case is going to be rather miniscule and will be deposited pretty evenly.

All I'm looking for is weight variation, not the actual weight of a clean case. A dirty case empty and a dirty case full of water. The differences are pretty graphic and if I want to go to all that trouble it gives me a good indication of the volume differences.

In reality, all I do is sample the cases I've already sorted dry. When I shoot a batch that I've segregated by weight when clean I then just verify that the capacities are relative to the even weights.

 

[Dynamic1]

Thank you for the clarification.

Much appreciated!

 

[1shot]

Jlow,
As I said in my post, I re-use the wax "pellet". I use a dental tool called a scaler and it takes it right out and doesn't leave any residue. Having said that, I may give Donovan's method a try as well.
Lloyd

 

[mikecr]

-I stand hand deprimed cases on a plastic golf tee into the flash hole. I could see how the wax would work well, and someone around here recently posted a machined plug/stand just for this operation(sort of a delrin pocket uniformer).
- I add a couple drops of any common Alcohol to a cup of water to reduce it's tension.
- I touch a tissue corner to any meniscus forming at case mouths to level.
- I test all cases fully fireformed(after 2-3 firings measured stable in dimension), unsized, and as they come from the smoking chamber other than hand deprimed and tumble cleaned in mild media.

My objective is to compare case to case H20 capacity -while cases are actually in a state where they are most likely to match, and cull out departures. I also get an accurate H20 capacity here for entry into my log & QuickLoad.
You should know, or someone should tell you, matched H20 capacity will not likely hold with FL sizing. This, regardless of case weights of coarse.

 

[Nomad47]

For actual case capacity, QuickLoad says to use FIRED cases that were fired in YOUR gun.

 

[thefitter]

Weigh with the meniscus concave and convex and then average.

 

[MVW]

Am I correct in assuming that you need to trim the fired cases to a common length?

 

[amlevin]

Am I correct in assuming that you need to trim the fired cases to a common length?

Yup! And to be technically correct you would also have to uniform all primer pockets and deburr flash holes. Any "variation" in the amount of metal in the case will affect the weight. To really go pick the fly feces out of the ground pepper, all extractor grooves should be "uniformed too". Good luck on that.

Those that measure with any powder or dry substitute also need to vibrate the material until it' fully settled. Otherwise there will be variations. Whether they matter or not?? Just pointing out some of the absurdities that are out there 8)

 

[mikecr]

Am I correct in assuming that you need to trim the fired cases to a common length?

Your fully fireformed cases will be same(in lot) in trim length, headspace, web & shoulder diameters, etc, provided you do not FL size or run hot loads until AFTER obtaining H20 capacities. If you have to FL size from the git-go, as is common with some cartridges, then your capacities will never really match anyway.
With this you're best bet is to run higher pressure loads(if you can)to reduce the impact of capacity variances. You're FL sizing anyway, so might as well.

I don't run hot loads. I don't FL size, so I don't have to trim, and rarely anneal.
My matched brass still matches after many reloads. I suspect this will continue indefinitely.
To do this, I stay away from cartridges that require FL sizing(like a 30-06).