Case Capacity

[338winmag]

Some manuals list the case capacity for powder loads. Since this is not listed by all, how can an estimate be made? Folr example, say I want to only use loads that are between 95% and 98%.

Is 100% case capacity considered base of bullet and base of neck?

Thanks
338winmag

 

[DrMike]

Powder density is measured against water, which is accepted as 1.000. Because powder can be compressed due to the physical dimensions of the powder, it is possible to load a case to higher than case capacity. One hundred percent case capacity is full, given the density of the powder. However, by filling the case by dropping through a long drop tube or seating the bullet carefully after tapping the powder down to fill the air spaces, you actually are able to fill (especially stick powders) to more than 100 percent of case capacity. Realistically, the only way to know for certain what your case capacity is, you need to measure a fired case from your own rifle. Deoxygenate water by letting it set uncovered overnight. Weight a fired case (tare), carefully fill it with water until you form a meniscus and weigh again to get the case capacity. At standard pressure and temperature (if at all possible, measure at 70 degrees and assume that air pressure where you are is sea level), the weight of the deoxygenated water is case capacity. Most powders will have a density between 85 and 97 percent of water at STP. After that extended explanation, I'd say to assume that if the base of your bullet is just touching the powder, you are at approximately 95 to 100 percent of case capacity.

 

[338winmag]

Setting the water out now.
Guess what I am doing tomorrow morning.

Thanks.
338winmag

 

[SJB358]

That is pretty interesting. Never knew that. Thanks for the lesson Mike. Scotty

 

[338winmag]

Okay the reason why I am doing this is to see if I can cut down on some possible "no-go" load scenarios costs - it will take some compilations over the rest of the year but it might be worth it.

Here is what I have for the following 270 Winchester:
Bullet - Speer Game King 160 gr SBT
Powder - 52 gr IMR 4350
Brass - Winchester
Primer - WLR
Seating Depth - 2.734 (.085 off the lands)
Velocity - 2881 FPS
Some of the easiest very consistent 1/2" groups @ 100 yards I have ever shot (I point and click :grin: )

Wet Weight - 394.5
Dry Weight - 337.2
Case Capacity - 57.3

Load Density - .9075 %

Thanks DRMike!

 

[sask boy]

I always wondered about that :lol: That for the information Mike.


Blesssings,
Dan

 

[BK]

Load Density - .9075 %

Not to get all anal-retentive German Virgo land surveyor math geek on you, but you are at 90.75%

 

[onesonek]

DrMike,,, isn't that also figuring that the base of the bullet will not be seated below the meniscus point? Or did I miss something?

 

[SJB358]

Okay the reason why I am doing this is to see if I can cut down on some possible "no-go" load scenarios costs - it will take some compilations over the rest of the year but it might be worth it.

Here is what I have for the following 270 Winchester:
Bullet - Speer Game King 160 gr SBT
Powder - 52 gr IMR 4350
Brass - Winchester
Primer - WLR
Seating Depth - 2.734 (.085 off the lands)
Velocity - 2881 FPS
Some of the easiest very consistent 1/2" groups @ 100 yards I have ever shot (I point and click :grin: )

Wet Weight - 394.5
Dry Weight - 337.2
Case Capacity - 57.3

Load Density - .9075 %

Thanks DRMike!

I imagine you meant a 150gr GK instead of a 160gr bullet Steve. Looks like a great load. Scotty

 

[338winmag]

Darn I made all sorts of typos. Thats what I get for trying to type and chew gum at the same time.

lol... damn that decimal point ....I read it as 90 % but wrote it as my calculator wrote it on anal-retentive German Virgo land surveyor math geek LCD.

As for the bullet - 150 Hornady Interlock

...and this is exactly why I don't play music when I am reloading.... :grin:

 

[onesonek]

DrMike,,, isn't that also figuring that the base of the bullet will not be seated below the meniscus point? Or did I miss something?

The reason I asked, is I do it slightly differently.
Back in the day before programs such as QuickLoad, and I was playing with new wildcats, I only had the Powley Slides to work with, in order to find starting loads where no data was available.
In doing so, one needed case capacity for the intended bullets seating depth.
The proceedure for that, was to seat the bullet to your desired OAL, in a unprimed case . Fired case was still desired so long as there was enough neck tension to hold. Otherwise partial sizing was in order. Weigh the case bullet and a small peice of scotch tape.
With a syringe, fill with water through the flashhole, (not filling the pocket), place the tape over the pocket to keep the water in and weigh again. This gave to capacity of a bullet and seating depths of each.

 

[338winmag]

Onesonek, with the exception of not using the tape, that is what I did to get this capacity and density information.

 

[DrMike]

isn't that also figuring that the base of the bullet will not be seated below the meniscus point?

This gives the capacity with the seated bullet. Since powder never has a density of 1.000, it always has less case fill. The volumetric capacity of the loaded case is useful, but QuickLoad (and calculations reprinted in reloading guides) are based on the density of the smokeless powder chosen and not solely on the volumetric measure of the loaded case. The measure I outlined yields case volume/

 

[onesonek]

Ok Doc,,don't know why, but somehow I missed that or didn't read the seated bullet into it. Which for the most part is common sense, I just wanted to confirm.
And I do understand and agree on the QL.

 

[atmoshpere]

OK sorry guys, but now I'm a little confused :?

Just to clarify what I think has been said, DrMike's original procedure described how to arrive at the empty case volume, while onesonek's procedure was for measuring available case capacity for a given bullet/seating depth combo in a given case...is that right?

Which number does quikload use? Is load density based off of empty case volume or loaded case volume? i.e. GR powder/empty case volume or GR powder/available case volume based on seating depth?

thanks,

atm

 

[DrMike]

Load density is calculated from internal case capacity. It is, to some extent, a number which has little meaning other than as a comparison to differing situations. In general, it is preferable to exclude as much air as possible from a case (95% fill ensures better ignition than 60% fill). Obviously, there is a point where the case is filled to such a point that compression becomes necessary. Ideal case fill is probably between 95 and 105%. Again, this is a number for comparison, and not for absolute calculations. Seating depths vary, brass thickness varies, chamber volumes vary--if one were to endeavour to work from an absolute value, it would be necessary each time you began a load to take each of these variables into account.

 

[onesonek]

Ah yes,,,sorry for the confusion, which is my fault. I kind of misread everything in general and somewhat confused myself. I was thinking more on the load density side.

 

[Oldtrader3]

Or if you want to be even more anal-retentive, Virgo, retired engineer (ahem), you can fill an unsized case to the neck and seat a bullet into the case to the depth level that you normally seat the bullet, letting the excess water run over the top, remove the bullet, dry the outside of the case and then weigh the water and case.

I have found that published data varies quite a bit from actual components.

 

[FOTIS]

Quickload baby!!!!!!!

Best investment I ever made. That and the chronograph.

 

[atmoshpere]

Quickload baby!!!!!!!

Best investment I ever made. That and the chronograph.

So can you change your COL on quickload, and if yes, does it show a pressure curve variance with seating depth changes?

thanks,

atm