Case Volume
- Thread starter hammer58
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Fire form the case to your chamber . Trim all to same length . Leave primers in and weigh a case . Then fill case with water to top of mouth ( level ) make sure no water drops are on the outside of the case and weigh the water filled case . Subtract the weight of the empty case from the weight of the water filled cases weight . The difference is your case volume .
Two things are a must . They need to be fire fomed and all should be the same length
Two things are a must . They need to be fire fomed and all should be the same length
polyphemus
New member
1g.=1cc
Distilled water is best.
Distilled water is best.
That is one way to do it, and its fine for your own reference. Do note that it is slightly different from the usual (standard) method, which is to fill the case with water to the base of the neck, not the case mouth.
Filling the case to the mouth with water, and weighing it WILL give you the entire volume of the empty case. It will NOT give you the volume available for powder. (which is what most of us are looking for when we measure).
The usual method is to fill to the base of the case neck, where the base of the "standard" bullet will be in the loaded round. Volume taken up by the bullet is not used when determining case powder volume/capacity.
Not sure just what value the information has, really. Other than to show you which cases have more or less volume than others, which is something that can be roughly determined by weighing the cases dry.
Sized and trimmed to all be the same dimensions on the outside, weight variations indicate which cases have thicker walls, and so, less internal volume.
For handloading, the actual measured volume doesn't matter as much as consistency of volume across the range of brass. That is one reason why we segregate our brass by weight (volume - with most, sorting by headstamp is good enough), so that each case in a batch is as close to the same as we can get it.
For example, you may find that in caliber A, WW cases hold 1.5gr more than R-P cases (on average), and therefore, for the most accurate ammunition, and remember that accuracy is dependent on consistency, you don't mix brands of cases in a batch.
For practicality, this applies to rifle cases more than pistol cases, but does apply to everything, to a degree. If your ammo is made to feed a high volume bullet spitter, where the idea is to get a lot of bullets in the target area rapidly, small variations in case capacity usually don't mean much.
If you goal is to put all your bullets in one hole (or as small a group as you can manage) then variations in case capacity can have a large effect.
Good Luck!
https://thefiringline.com/forums/showthread.php?t=492139 I sort same lot/brand by weight , after prep.
Ok, I am a bit crabby this morning and am somewhat short, but
I contend its a waste of time.
Anything with water and a cylinder produces convex meniscus and that hard to zero out.
Bottom of the shoulder, good luck in looking down there and getting that consistent along with the meniscus issue.
fill with a very fine power and settle it is probably the most reliable (748)
and in the end, case volume makes so little difference as to be irrelevant.
If its that important, get Lapua, sort by weight and then go on.
We are talking about sub .250 moa holes at best here though.
I contend its a waste of time.
Anything with water and a cylinder produces convex meniscus and that hard to zero out.
Bottom of the shoulder, good luck in looking down there and getting that consistent along with the meniscus issue.
fill with a very fine power and settle it is probably the most reliable (748)
and in the end, case volume makes so little difference as to be irrelevant.
If its that important, get Lapua, sort by weight and then go on.
We are talking about sub .250 moa holes at best here though.
44 :
Although i understand your point i've not heard to only fill to the neck . That to me seems like you're just asking for variences in the volume because it's a judgement call as to where to stop . In a large case i could see a varience of +/- one or two drops which will not happen if you fill level to the case mouth .
The more think about it , to the neck does not seem right . The link above with the chart of case volumes . The 308 says 56gr the only cases i've measured that weighed that much was Winchester . My LC case are in the 54.5 to 55 gr area and thats filling to the top . So if i were to only fill to the neck/top of the shoulder . They would likely be around 50gr . Then there's uncle nick always talking about overflow volume measurement . I beleave Quickloads uses the overflow method as well . Are you sure your method is the standard way of measuring case volume ?
Although i understand your point i've not heard to only fill to the neck . That to me seems like you're just asking for variences in the volume because it's a judgement call as to where to stop . In a large case i could see a varience of +/- one or two drops which will not happen if you fill level to the case mouth .
The more think about it , to the neck does not seem right . The link above with the chart of case volumes . The 308 says 56gr the only cases i've measured that weighed that much was Winchester . My LC case are in the 54.5 to 55 gr area and thats filling to the top . So if i were to only fill to the neck/top of the shoulder . They would likely be around 50gr . Then there's uncle nick always talking about overflow volume measurement . I beleave Quickloads uses the overflow method as well . Are you sure your method is the standard way of measuring case volume ?
There are two measures of capacity:
Case Water Capacity, the amount of space for powder under the bullet in grains of water weight.
and,
Case Water Overflow Capacity, the total internal capacity of the case up to the case mouth, but, despite the name, with no meniscus and no actual overflowing of water. The name just means that adding more water would start to overflow the case.
What Metal God described is the latter. It is used in QuickLOAD to determine Case Water Capacity by subtracting the volume of bullet insertion from it. It is a less messy way to make an accurate determination. The direct way to accurately determine Case Water Capacity is to weigh a dry fired case and a new bullet. Then fill the case with water, insert a bullet to its actual seating depth, squirting water all over, then wiping the excess water off and weighing the case, bullet and water to subtract the dry case and bullet weight from. This method takes into account boat tails and other source of bullet shape error that might exist.
True at 4°C (39.2°F), where water is most dense. At room temperature it is closer to 0.9977 g/cc. Not usually significant when you compare two very similar cases, but for the sake of completeness I'll put it here. At the sea level boiling point (100°C (212°F)), the density of water has dropped 4.139% to 0.9586 g/cc. A fluid ounce is the volume of 1 ounce of water that hot, if you ever wondered why fluid ounces weigh 4% more than an actual ounce at room temperature.
In interior ballistics in the U.S., grains of water by weight are used for both kinds of case capacity. There are 15.43236 grains in a gram, if you need to convert.
Case Water Capacity, the amount of space for powder under the bullet in grains of water weight.
and,
Case Water Overflow Capacity, the total internal capacity of the case up to the case mouth, but, despite the name, with no meniscus and no actual overflowing of water. The name just means that adding more water would start to overflow the case.
What Metal God described is the latter. It is used in QuickLOAD to determine Case Water Capacity by subtracting the volume of bullet insertion from it. It is a less messy way to make an accurate determination. The direct way to accurately determine Case Water Capacity is to weigh a dry fired case and a new bullet. Then fill the case with water, insert a bullet to its actual seating depth, squirting water all over, then wiping the excess water off and weighing the case, bullet and water to subtract the dry case and bullet weight from. This method takes into account boat tails and other source of bullet shape error that might exist.
polyphemus said:
True at 4°C (39.2°F), where water is most dense. At room temperature it is closer to 0.9977 g/cc. Not usually significant when you compare two very similar cases, but for the sake of completeness I'll put it here. At the sea level boiling point (100°C (212°F)), the density of water has dropped 4.139% to 0.9586 g/cc. A fluid ounce is the volume of 1 ounce of water that hot, if you ever wondered why fluid ounces weigh 4% more than an actual ounce at room temperature.
In interior ballistics in the U.S., grains of water by weight are used for both kinds of case capacity. There are 15.43236 grains in a gram, if you need to convert.
I disagree . so separating brass by head stamp is a waist of time since case volume does not matter . Some manufacturers have significantly different case volume then others in the same cartridge . I recently compared LC-14 case to some Winchester cases that were bought new a couple years ago . The case weight difference was almost 20gr and the case volume difference was 2.5 to 3gr difference . You will get significantly different results loading the same components to the same spec in those two cases .
What about this :
I'm not sure which manufacture Winchester or Federal but one of them in the 60's or 70's could be later had some very thin walled 308 cases that weighed in the 150gr area maybe a tad less . I don't have any but have read that there case volume was quite a bit more then recent production from the same manufacturer . So if you had an old load you worked up in the 70's that was at max pressure with that brass then tried to load that same charge/load in there most recent brass . It could get dangerous real fast . It's the same head stamp so why work a new load up , right ?
A brother of mine was doing some QuickLoad work for me.This is what he asked me to do for case volume as an input for QL.
Note the point here is the actual volume of the combustion chamber at firing.
I do not recall whether he said as fired or sized.Its been a while.
I'm going to propose sized,for a reason I will explain later.You will need a primer in place,fired is fine.
Take the bullet you will use and file a flat on it the length of the cylindrical body.Not extreme,but enough so water can leak out under pressure.
Weigh the case and the filed bullet.
Then fill the case with water,and seat the bullet to the length you will load.
Go slow,and let the water vent out.
Now weigh the water filled assembly.No maniscus issue,and you have allowed for the space the bullet takes up.
My reasoning on using sized brass,(which may be wrong.I'll see what Uncle Nick says)
The burn /pressure curve is well under way before the case expands fully.
And the bullet jumping forward adds to volume.
You have to start someplace.So long as you do it the same way each time,sized with the bullet seated represents conditions at ignition.
Note the point here is the actual volume of the combustion chamber at firing.
I do not recall whether he said as fired or sized.Its been a while.
I'm going to propose sized,for a reason I will explain later.You will need a primer in place,fired is fine.
Take the bullet you will use and file a flat on it the length of the cylindrical body.Not extreme,but enough so water can leak out under pressure.
Weigh the case and the filed bullet.
Then fill the case with water,and seat the bullet to the length you will load.
Go slow,and let the water vent out.
Now weigh the water filled assembly.No maniscus issue,and you have allowed for the space the bullet takes up.
My reasoning on using sized brass,(which may be wrong.I'll see what Uncle Nick says)
The burn /pressure curve is well under way before the case expands fully.
And the bullet jumping forward adds to volume.
You have to start someplace.So long as you do it the same way each time,sized with the bullet seated represents conditions at ignition.
CW, if you are finding the volume for QL, that ain't gonna work.
As has been pointed out, you use fired in your rifle cases, trimmed the same, and filled to top. Even then they may require trimming again after you re-size them, if you want them to be the same length that is.
If you want to experiment, take 10 random fired cases from a batch of the same
headstamp and weigh them and write the weight on the sides, then do the water volume test and note the results for each case. To be as accurate as you can you need to measure water volume three times and average the results for each case.
See if you find the correlation.
Sounds like a perfectly good way to destroy a lot of time, me, I'm gonna go practice.
As has been pointed out, you use fired in your rifle cases, trimmed the same, and filled to top. Even then they may require trimming again after you re-size them, if you want them to be the same length that is.
If you want to experiment, take 10 random fired cases from a batch of the same
headstamp and weigh them and write the weight on the sides, then do the water volume test and note the results for each case. To be as accurate as you can you need to measure water volume three times and average the results for each case.
See if you find the correlation.
Sounds like a perfectly good way to destroy a lot of time, me, I'm gonna go practice.
Still crabby and argumentative.
Somewhere thre was a link about that.
the end result was tht it make little differne, its a minsiucle affect fo racauly powedr fill.
I do sort by case, but only because its possible the case may rteacti diffetnt from brand to brand.
So lets reduce this to details.
Are we filling the case up to the top? Nope.
Are we filling it to the shoulder (maybe)
Compressed load, maybe a factor but for most?
So the case winds up with a bit more empty than the other one, they both hold the same amount of powder if measured accurately.
Bench rest shooters dump in by powder measure.
I would guess (from the link) this is down in the number 30 position as significant factors that affect the accuracy of a load.
anyone take two extreme cases mfg by weight, , weigh in the same amount of power and see what the velocity difference is?
Somewhere thre was a link about that.
the end result was tht it make little differne, its a minsiucle affect fo racauly powedr fill.
I do sort by case, but only because its possible the case may rteacti diffetnt from brand to brand.
So lets reduce this to details.
Are we filling the case up to the top? Nope.
Are we filling it to the shoulder (maybe)
Compressed load, maybe a factor but for most?
So the case winds up with a bit more empty than the other one, they both hold the same amount of powder if measured accurately.
Bench rest shooters dump in by powder measure.
I would guess (from the link) this is down in the number 30 position as significant factors that affect the accuracy of a load.
anyone take two extreme cases mfg by weight, , weigh in the same amount of power and see what the velocity difference is?