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Rifle cases water capacity? Why?
- Thread starter Chainsaw.
- Start date
Yosemite Steve
New member
FrankenMauser, did you take any other measurements on those cases? Case to shoulder, total case length, sized, partial sized, unsized, etc?
Reloadron, thank you for that data. It kind of supports my thoughts on water weight. Given all things are prepped the same way the consistency of the brass weight is proportional to the case volume with a small margin of error(mostly). The time it takes to weigh water is redundant to me unless I were going to compete. It is a given that all of the other case preparations need to be done for consistency. IF those preparations are done well and the cases have been weighed for me the extra step of weighing the water in them is redundant. I have not checked volumes of every case but when I have the difference is equal +or- .1 grain max. Doing a simulation in Quickload with a 30-06 at max load with 4064 it's about 1.5 fps difference per .1 grain of water volume. This tells me that the volume is indeed significant but is it worth the extra hassle? Yes if I am going to compete. All of the other work I have done insures that my case volumes will be uniform.
The single most important step is lot segregation from the beginning. Then consistent handling and case preparation from sizing to seating the primers. It is an anal retentive paradise!
Reloadron, thank you for that data. It kind of supports my thoughts on water weight. Given all things are prepped the same way the consistency of the brass weight is proportional to the case volume with a small margin of error(mostly). The time it takes to weigh water is redundant to me unless I were going to compete. It is a given that all of the other case preparations need to be done for consistency. IF those preparations are done well and the cases have been weighed for me the extra step of weighing the water in them is redundant. I have not checked volumes of every case but when I have the difference is equal +or- .1 grain max. Doing a simulation in Quickload with a 30-06 at max load with 4064 it's about 1.5 fps difference per .1 grain of water volume. This tells me that the volume is indeed significant but is it worth the extra hassle? Yes if I am going to compete. All of the other work I have done insures that my case volumes will be uniform.
The single most important step is lot segregation from the beginning. Then consistent handling and case preparation from sizing to seating the primers. It is an anal retentive paradise!
Yosemite Steve
New member
considering the volume of gas generated from the explosion of the powder I don't think a grains worth of water volume would amount to a gnats fart in a hurricane
I guess if a gnat was in a hurricane he would be flying pretty fast and the potential 25 fps a grains worth of water volume would change would not catch up to said gnat. Point taken.
Long ago the NRA technical guru Wm. C. Davis, Jr. suggested 1 grain of powder for every 16 grains of brass weight. Brass is about 8.5 times heavier than water, so that's .53 grains of powder for each grain of water capacity difference assuming the weight difference is entirely due to the amount of brass in the body where the capacity is. My experiments say that is about right for keeping velocity constant so it may be a best for long range, but it lets barrel time get longer as capacity goes up, and you may find you need as much as 0.7 grains of powder for each grain of added space to maintain barrel time. That number will also keep peak pressure pretty constant with most rifle powders.
But do keep in mind that you can change the weight of a .308 or 30-06 casehead over 6 grains just by going from minimum to maximum linear dimensions and extractor groove relief angles without changing the body or its water capacity at all. So Davis's estimate can be foiled if you just rely on weight. You really have to measure case water overflow capacity to be sure of what you have. I've had cases that came off 6 distinct sets of tooling (six lumps in the weight distribution).
Keep in mind that at shorter ranges there isn't much difference in drop due to velocity variation, so keeping the barrel time tuned probably matters most. But if you are shooting long range, see if you can establish a sweet spot that covers the biggest range of capacities you have with the charge adjusted by Davis's estimate to keep velocity more constant.
Overall, as well, you can sometimes find quite wide sweet spots and those let you ignore adjust for variation until you are at very long range where the velocity difference starts to show up.
But do keep in mind that you can change the weight of a .308 or 30-06 casehead over 6 grains just by going from minimum to maximum linear dimensions and extractor groove relief angles without changing the body or its water capacity at all. So Davis's estimate can be foiled if you just rely on weight. You really have to measure case water overflow capacity to be sure of what you have. I've had cases that came off 6 distinct sets of tooling (six lumps in the weight distribution).
Keep in mind that at shorter ranges there isn't much difference in drop due to velocity variation, so keeping the barrel time tuned probably matters most. But if you are shooting long range, see if you can establish a sweet spot that covers the biggest range of capacities you have with the charge adjusted by Davis's estimate to keep velocity more constant.
Overall, as well, you can sometimes find quite wide sweet spots and those let you ignore adjust for variation until you are at very long range where the velocity difference starts to show up.
I am not a long range shooter and satisfied with sub MOA groups. Most my loads are .5" to .8" groups and that is great for me. I only sort brass by head stamp. The best examle i can give you would be when i load my 243. I mostly have Hornady brass that i use and load them in batches of 50. Last time i loaded i got 2 barnes brass cases mixed in. I was loading powder and my normal load was well below neck and an uncompressed load in the Hornady brass. When i unknowingly dropped the powder in the Barnes brass i saw the power up in the neck. I removed these but if i would have continued, my loads would have been compressed and sure it would of effected pressure and velocity of the load.
For accuraccy i try to achieve water capacity is totaly unnecassary. Now my buddy who is a long range nut and measures success by .1" goes to the extreame. Every case is weighed, measured, trimmed, concentricity check, water volume, primer seat depth uniformed, flash hole deburred, annealed, before it is ever loaded. When he gets a new batch of brass 10-20% will not make the cut and gets tossed. Im there collecting the scraps and getting 3/4" groups with them. And that is just the brass before loading starts, he gets even more extreame when the loading starts.
Its all relative to your desired level of accuracy or OCD.
For accuraccy i try to achieve water capacity is totaly unnecassary. Now my buddy who is a long range nut and measures success by .1" goes to the extreame. Every case is weighed, measured, trimmed, concentricity check, water volume, primer seat depth uniformed, flash hole deburred, annealed, before it is ever loaded. When he gets a new batch of brass 10-20% will not make the cut and gets tossed. Im there collecting the scraps and getting 3/4" groups with them. And that is just the brass before loading starts, he gets even more extreame when the loading starts.
Its all relative to your desired level of accuracy or OCD.
I guess if a gnat was in a hurricane he would be flying pretty fast and the potential 25 fps a grains worth of water volume would change would not catch up to said gnat. Point taken.
get case volume the add in the barrel volume and can use Boyles Law if you want to know the volume of gas and generated to raise the pressure to 40 - 50 K pressure in about .002 seconds.
I did case volumes for a while then figured out it did not matter at all
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FrankenMauser
New member
4.0 gr H2O, or 7.5% -- as noted in my post.So Frankenmauser, on you 307 brass, the ones that weighed 160grains vs the ones that weighed 180 grains. What was the h2o capacity difference?
Sizing, case prep, and critical dimensions were all the same.FrankenMauser, did you take any other measurements on those cases? Case to shoulder, total case length, sized, partial sized, unsized, etc?
An additional note:
Hornady's newly-released .307 Win brass weighs in at 170 gr, out of the box, with a FL-sized case capacity of 55.0 gr H2O (overflow). (2.007" case length - I trim W-W to 2.003".)
I believe the capacity will increase after the initial firing, as my sizing die didn't so much as touch the body or shoulder of the cases I sized. My educated guess is 56.0 gr...
As mentioned by others previously, 'fire-formed' case volume is more important ... but I don't have a fire-formed sample of each case, yet.
Yosemite Steve
New member
get case volume the add in the barrel volume and can use Boyles Law if you want to know the volume of gas and generated to raise the pressure to 40 - 50 K pressure in about .002 seconds.
I was lazy and use quick Load.
weighed them on a scale abd they are ALL with in 5 grains.
That's craptastic brass.
Overall, as well, you can sometimes find quite wide sweet spots and those let you ignore adjust for variation until you are at very long range where the velocity difference starts to show up.
when the average reloader is using a scale whose accuracy is plus or minus a tenth of a grain why bother with water capacity. The burning powder will be generating several cubic feet of gas to fill that volume before the bullet exits the barrel.
Then they measure the powder to plus or minus a tenth on the same scale. Whatever you measure is of dubious accuracy be it water or powder on even the higher priced scales that use a load cell. If you want or need a consistent velocity the best way to get it is finding a node with a .3 grain or better span
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I have to get to the note taking and data collection, just curiosity not driven by it.
For the most part (and its an assumption) weight is due to volume and the average deviation is 5 grains wide. Take that into 16 and we have 3.
So that is the possible variance in the load (and throw in all those other factors?)
I will just stick with accurate powder dispensing and common cases.
For the most part (and its an assumption) weight is due to volume and the average deviation is 5 grains wide. Take that into 16 and we have 3.
So that is the possible variance in the load (and throw in all those other factors?)
I will just stick with accurate powder dispensing and common cases.
Coming back to your opening question: "I get the point of using water capacity to measure cases volumetric capacity but, my question is when should the practice be applied?"
I have only been loading for a lil over 60 years.... ya I am an old bum..... and I can say I have never worried about case volume. Good grief, clean them up, load them and have fun shooting them!
I have only been loading for a lil over 60 years.... ya I am an old bum..... and I can say I have never worried about case volume. Good grief, clean them up, load them and have fun shooting them!
Coming back to your opening question: "I get the point of using water capacity to measure cases volumetric capacity but, my question is when should the practice be applied?"
I did not spend a lot of time measuring and weighing cases; I did find cases that that were different. Reloaders claim military cases are heavier and they used deductive reasoning to convince other reloaders the case was thicker because it was heavier. I have military 30/06 cases that have a case head thickness of .200", I have R,P. cases with case head thickness of .260". SO? The commercial case has a thick case head and the military case head has a thin case head. If that is true I have military cases that have thick case bodies and commercial cases with thin case bodies.
And then if that makes any difference the powder columns are different. The military case has a long powder column that is small in diameter and the commercial case has a short powder column that is larger in diameter.
The case with the thick case head is the safest if there is any truth to the rumors I have heard about case head protrusion and unsupported case head.
F. Guffey
reynolds357
New member
I am not too convinced that case volume matters much.
I was using mismatched brass to develop loads for my son's 7-08. I got 6 ft sec max deviation over 20 shots using 3 different brands brass. I have never gotten close to that with my 6PPC, 6BR, or 30 BR using match prepped brass.
I was using mismatched brass to develop loads for my son's 7-08. I got 6 ft sec max deviation over 20 shots using 3 different brands brass. I have never gotten close to that with my 6PPC, 6BR, or 30 BR using match prepped brass.