Rifle cases water capacity? Why? - Page 2

Yosemite Steve · February 20, 2018, 08:16 PM

Quote:

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.

**Unclenick** · February 20, 2018, 08:35 PM

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.

Troy800 · February 20, 2018, 08:55 PM

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.

hounddawg · February 20, 2018, 10:17 PM

Quote:

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

FrankenMauser · February 20, 2018, 11:20 PM

Quote:

So Frankenmauser, on you 307 brass, the ones that weighed 160grains vs the ones that weighed 180 grains. What was the h2o capacity difference?

4.0 gr H2O, or 7.5% -- as noted in my post.

Quote:

FrankenMauser, did you take any other measurements on those cases? Case to shoulder, total case length, sized, partial sized, unsized, etc?

Sizing, case prep, and critical dimensions were all the same.

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 · February 20, 2018, 11:28 PM

Quote:

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.

jimbob86 · February 21, 2018, 01:08 AM

Quote:

weighed them on a scale abd they are ALL with in 5 grains.

That's craptastic brass.

F. Guffey · February 21, 2018, 11:50 AM

Quote:

You risk taker you.

And I ask: What is the risk?

F. Guffey

hounddawg · February 21, 2018, 12:32 PM

Quote:

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

RC20 · February 21, 2018, 04:45 PM

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.

Mobuck · February 21, 2018, 06:06 PM

"I get the point of using water capacity to measure cases volumetric capacity but"

All it does is COMPARE the volumeric capacity. You're going have to be a VERY experienced reloader and shooter for a FEW grains of internal capacity to be relevant.

jamaica · February 21, 2018, 06:43 PM

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!

F. Guffey · February 22, 2018, 09:08 AM

Quote:

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

F. Guffey · February 22, 2018, 09:13 AM

And again I ask; "What is the risk?

F. Guffey

reynolds357 · February 22, 2018, 04:06 PM

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.

**Unclenick** · February 22, 2018, 04:50 PM

It really depends on the brass. As Houdawg says, if you are trying to match to a tenth of a grain, you are wasting your time. But some brass varies a lot. .300 Win Mag brass with as little as 87.5-grain water overflow capacity can be had (Tula) and brass with as much as 95.5 grains of water overflow capacity can be had (Norma). It's enough that QuickLOAD's author made the different brands of 300 Win Mag brass different cartridges in the database. A nearly 9% spread in capacity is too much to ignore if you want to be hitting a target 1000 yards away.

.308 is more uniform in volume now than it used to be. So is .30-06. A 1981 NRA book I have mentions a .30-06 Peters case that weighed 215 grains. LC is usually 95-ish

Here's a chart made up from some WW .308 Win brass I bought bulk at Camp Perry one year. There are a few that were off the edge of the chart, with the lightest being 153.5 grains and heaviest 159.5 grains. I also measured these for neck wall runout and found one with a whopping 0.008" TIR, but the second worst was half that bad and most averaged around 0.002". You can see four distinct bell curves, each representing distribution around an average for a particular set of tooling, so I don't expect uniformity here.

Here is a much smaller sample of Lapua .308 brass. You see it is much tighter and it is unlikely a load adjustment would be needed.

F. Guffey · February 22, 2018, 05:30 PM

And then there was the shooter/reloader/writer of everything gun related. He purchased 500 cases from one manufacturer from what he believed to be 'one lot'. He sorted and separated, shot and sorted and separated again until he settle on 43 cases that were perfect.

He then started over sorting and separating and matching the culls. With some of his culls he shot one hole groups by indexing the cases in the chamber. All of this happened over 47 years ago.

F. Guffey

jamaica · February 23, 2018, 01:03 PM

"I get the point of using water capacity to measure cases volumetric capacity but, my question is when should the practice be applied?"

This onery ol man is gonna say: Forget it! Shine em up, load em up and go shoot em. Have fun! But then I have only been reloading for 63 years, what do I know?

February 20, 2018, 08:35 PM	#27
Unclenick Staff Join Date: March 4, 2005 Location: Ohio Posts: 21,063	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. __________________ Gunsite Orange Hat Family Member CMP Certified GSM Master Instructor NRA Certified Rifle Instructor NRA Benefactor Member and Golden Eagle

February 21, 2018, 04:45 PM	#35
RC20 Senior Member Join Date: April 10, 2008 Location: Alaska Posts: 7,014	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. __________________ Science and Facts are True whether you believe it or not

February 22, 2018, 04:50 PM	#41
Unclenick Staff Join Date: March 4, 2005 Location: Ohio Posts: 21,063	It really depends on the brass. As Houdawg says, if you are trying to match to a tenth of a grain, you are wasting your time. But some brass varies a lot. .300 Win Mag brass with as little as 87.5-grain water overflow capacity can be had (Tula) and brass with as much as 95.5 grains of water overflow capacity can be had (Norma). It's enough that QuickLOAD's author made the different brands of 300 Win Mag brass different cartridges in the database. A nearly 9% spread in capacity is too much to ignore if you want to be hitting a target 1000 yards away. .308 is more uniform in volume now than it used to be. So is .30-06. A 1981 NRA book I have mentions a .30-06 Peters case that weighed 215 grains. LC is usually 95-ish Here's a chart made up from some WW .308 Win brass I bought bulk at Camp Perry one year. There are a few that were off the edge of the chart, with the lightest being 153.5 grains and heaviest 159.5 grains. I also measured these for neck wall runout and found one with a whopping 0.008" TIR, but the second worst was half that bad and most averaged around 0.002". You can see four distinct bell curves, each representing distribution around an average for a particular set of tooling, so I don't expect uniformity here. Here is a much smaller sample of Lapua .308 brass. You see it is much tighter and it is unlikely a load adjustment would be needed. __________________ Gunsite Orange Hat Family Member CMP Certified GSM Master Instructor NRA Certified Rifle Instructor NRA Benefactor Member and Golden Eagle

February 20, 2018, 08:55 PM	#28
Troy800 Senior Member Join Date: December 25, 2015 Posts: 118	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.

February 21, 2018, 06:06 PM	#36
Mobuck Junior member Join Date: February 2, 2010 Posts: 6,846	"I get the point of using water capacity to measure cases volumetric capacity but" All it does is COMPARE the volumeric capacity. You're going have to be a VERY experienced reloader and shooter for a FEW grains of internal capacity to be relevant.

February 21, 2018, 06:43 PM	#37
jamaica Senior Member Join Date: March 24, 2006 Location: Northern Utah Posts: 705	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!

February 22, 2018, 09:13 AM	#39
F. Guffey Senior Member Join Date: July 18, 2008 Posts: 7,249	And again I ask; "What is the risk? F. Guffey

February 22, 2018, 04:06 PM	#40
reynolds357 Senior Member Join Date: December 10, 2012 Posts: 6,165	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.

February 22, 2018, 05:30 PM	#42
F. Guffey Senior Member Join Date: July 18, 2008 Posts: 7,249	And then there was the shooter/reloader/writer of everything gun related. He purchased 500 cases from one manufacturer from what he believed to be 'one lot'. He sorted and separated, shot and sorted and separated again until he settle on 43 cases that were perfect. He then started over sorting and separating and matching the culls. With some of his culls he shot one hole groups by indexing the cases in the chamber. All of this happened over 47 years ago. F. Guffey

February 23, 2018, 01:03 PM	#43
jamaica Senior Member Join Date: March 24, 2006 Location: Northern Utah Posts: 705	"I get the point of using water capacity to measure cases volumetric capacity but, my question is when should the practice be applied?" This onery ol man is gonna say: Forget it! Shine em up, load em up and go shoot em. Have fun! But then I have only been reloading for 63 years, what do I know?