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JerryK
11-21-2009, 07:41 PM
I'm running a 6.5x47 Ackley Improved, and would like to measure the case capacity to compare it to the stock cartridge. Everyone talks about grains of water, but what's a good method of adding/measuring/weighing? Just fill them both and weigh them?

John Kielly
11-21-2009, 07:50 PM
Water or any other liquid are a pain to mess around with. You end up having to hope you don't get bubbles, loading them up to the same place case to case can be problimatic & then you have to weigh the buggers & calculate volumes from that - or just use the weight alone.

A quick method to compare relative volumes that isn't all that inaccurate for most purposes is to use a fine grain ball powder & weigh that. You need to use a filling technique that's consistent, but any Lee manual will tell you how to do that. I still have a little jar of BLC-2 that packs close & seems to be pretty repeatable, but the powder choice is yours.

Pete Wass
11-21-2009, 08:48 PM
I'm running a 6.5x47 Ackley Improved, and would like to measure the case capacity to compare it to the stock cartridge. Everyone talks about grains of water, but what's a good method of adding/measuring/weighing? Just fill them both and weigh them?

(Weigh each case empty and record that weight.)

to use the water, turn on the kitchen faucet to just very small stream. Hold the caese under it until they are full with a slight crown on top of the neck is prescribed but it doesn't matter much for your purposes. Weight them full and subtract the empty weight from the full weight. You then have the difference in terms of liquid measure. A grain is a grain is a grain in terms of volume but I doubt water will weigh the same as powder.

Shake the cases vigorously to get the water out. OH, if it isn't obvious, you will need a spent primer in the cases to keep the water in. When you punch out the primers the cases to dry out readily. If you need to use them in a hurry warm them up on the kitchen range or with a hair dryer.

Ackman
11-21-2009, 09:36 PM
With water, I use a medicine dropper and some care so a bubble doesn't form under the shoulder. Also check the water level at casemouth under magnification to make sure it's exactly the same each time. It doesn't take long to get a feel for it and they come out ok.

Even with really fine grained powder it's difficult getting consistent - reliable - results. Drop it in very slowly. One thing that might also work is fine silica sand, but I've never tried it.

Donald
11-21-2009, 09:39 PM
Use an empty case with dud primer, sized because that is the way you will load it. Get a small syringe and some water with a touch of alcohol or soap to reduce the surface tension. Draw some water into the syringe and put the needle down to the bottom of the case. Push on the plunger and fill the case. No bubbles and the meniscus should be pretty flat. That should be just about the most accurate way. Just my opinion.

Donald

Tony Shankle
11-21-2009, 09:53 PM
I water weigh one time when I come up with a new wildcat but it never means anything. In my opinion it gives you info you can't use.

I like to weigh with powder. I try several different powders and record each one before I go into testing. It always amazes me how different powders have different volumes...holds 46 grains of one but 49 grains of another. This info helps me narrow down which one give me load density at the desired velocity and sometimes saves me a little work and barrel wear.

That darn water packs in there pretty tight! :D

Rick B
11-22-2009, 02:21 PM
If you do use water, I would suggest adding a little bit of dish washing detergent to it. It reduces the surface tension so that you do not get the "bubble" (meniscus) (http://en.wikipedia.org/wiki/Meniscus) at the case mouth which is both inaccurate and somewhat inconsistent.

As for technique, the eye dropper suggestion is a good one. Try it several times until you are confident you are getting a consistent result. Then you can plug the numbers into whatever software you are using.

mikecr
11-22-2009, 04:02 PM
Stand empty cases(on your scale) on a plastic golf tee pushed into the flash hole. Zero the scale.
Use an dropper and water as mentioned with a drop of alcohol.
If needed, touch a corner of tissue to flatten the meniscus(crescent).

I've checked hundreds of cases this way

Louis Boyd
11-22-2009, 09:50 PM
IAs for technique, the eye dropper suggestion is a good one. Try it several times until you are confident you are getting a consistent result. Then you can plug the numbers into whatever software you are using.

I use a case that's been fired in the chamber I'll be using the brass in and leave the spent primer in place. What I'm trying to measure is the volume the case will be at pressure in the chamber, not the volume of a new case. I use a syringe with a needle instead of a dropper. It's easy to add or remove water less than one drop at a time. Start filling by putting the needle through the flash hole into the primer so it will drive trapped air out of the primer. Once the needle is under the surface of the water already in the case it can't make bubbles as more water is squirted in rapidly. . I set a light so I can see the reflection of the light off of the water in the neck and adjust the fill until the reflection appears flat, neither concave or convex.

Before filling I put the case on a digital scale and record its weight then zero the scale with the case on it. After the water is added to the case the scale directly reads the volume in grains of H2O. The case is drained set aside to be deprimed and reloaded with other brass. The whole process takes little effort and no calculations.

Don
11-22-2009, 10:20 PM
Ive heard that mercury is the quickest, easiest, and most accurate to use for measuring case volume.

Ive never tried it..........not easily available and hard to dispose of properly when no longer needed. Wonder if there is something similar that easily available, store, and dispose of?.......Don

Steve Shelp
11-25-2009, 06:53 AM
lots of good suggestions but one very critical one has been missed:

- make sure your water (with dish detergent in it) is room temperature along with the cases you are measuring!!!


also

- to help reduce the formation of bubbles I don't use a syringe but a good old fashion straw that will fit though the neck of the case you are mearsuring. Have a tall glass of room temp water/detergent and insert the straw all the way to the bottom of the glass. Put your finger over the top of the straw and then insert the straw all the way into the bottom of the case and pull your finger off and the water will fill in from the bottom up without touching the sidewalls of the case as you withdraw the straw. You will need to experiment with how tall the water is in the glass so that you do not over fill a case.

- once the water forms a convex droplet in the mouth of the case, just use toilet paper and briefly touch the droplet to draw water out. It was mentioned above that at some point the water will become level and if you look straight down into the case and the water is perfectly level the water litterly disappears so you can't see it. If you see any light refraction and get a mirror image of anything the water is still forming a convex or concave droplet and you need to add or delete water accordingly.

Now does this give you a true volume reading... no. because it also measure the volume of the neck. But if you are improving a case it will give the % of increase capacity. So its helpful, but not the end-all-solve-all for true case capacity. So take it for what its worth.

Steve

mikecr
11-25-2009, 07:27 AM
And why would anyone need true case capacity?

We get exactly what we need from h20 capacity checks. A relative comparison from case to case, lot to lot. And if you you use QuickLoad, you can enter your measured capacity(to the mouths), and your resultant velocity, and calibrate the powder file. QL accounts for the volume of your entered bullet seating.