Case capacity by brand can vary by 8 Graines!!! - Page 3

Reloadron · March 30, 2017, 01:32 PM

Don, thanks for the tip. The primer pockets were a PITA to say the least.

I started with candle wax which did work but settled on the clay as I could weigh each small ball before using the stuff.

Funny you mentioned the lathe. Before I retired I had an entire small prototyping machine shop at my disposal.Unfortunately when I retired I lost access to that stuff. Can't say I miss going to work daily but I sure miss that machine shop and some of the best machinist and mechanical engineers to answer my questions.

Those 50 cases are all cleaned and primed. During the next few days powder and bullets and hopefully good weather to shoot.

Ron

Nvreloader · April 1, 2017, 03:39 PM

Reload Ron

Glad I could help, in a small way.

Tia,
Don

Don Fischer · April 1, 2017, 05:34 PM

Well I figured out where I went wrong. Title say's case capacity! Actually it's the case's themselves that vary as much as 8 grs.

Stats Shooter · April 1, 2017, 09:39 PM

No Don,

You were correct the first time. The volume, as in how much water I can fill a .300 win mag case with, can vary by 8 graines from brand to brand.

**Unclenick** · April 3, 2017, 09:57 AM

Yes. It seems only to be true in .300 WM, but case water capacity is measured in grains of water weight in this country, and those are the grains being referred to. If a case is made from 72:28 brass, like Norma's, the case weight difference should be about 68 grains if exterior dimensions match exactly. I've got .308 cases that are almost 40 grains different, so that is not an unimaginable number in the larger case.

Reloadron · April 3, 2017, 11:51 AM

Confusion? I think maybe a little confusion may stem from the units. Grans for example are a unit of weight and like grams are not something we associate with volume. That said we can make a connection in that 1.0 gram of pure water at a given temperature will occupy a volume of 1.0 cc (cubic centimeter). This makes for a convenient path from grains or grams units of weight to a unit of volume.

gr = grains
g = grams

1.0gr= 0.06479891g
1.0g = 15.4324gr

grams x 15.432 = grains
grains / 15.432 = grams

1.0g of water = 1.0cc of Volume.

So when we say 8.0 grains of water we are actually looking at 8.0 * .0648 = 0.5184cc of volume. How much powder is that? Well, that depends on the powder. All powders have a different VMD (Volume Metered Density). While a pound of lead and a pound of water weigh the same they will have different volumes. This is what the Lee Dippers are based on with the Powder VMD Associated Chart, the density of the powder determining the weight per unit of volume.

Example:

If a powder has a VMD of .1064 , and the desired charge weight is 4 grains,

4 x .1064 = .4256, or . 43 cc's

Charge Weight (grains) * VMD = Volume in cc

That formula can be manipulated however we choose to solve for the unknown.

If in the above the Volume (expressed in cc) is known and the VMD is known the weight can be calculated (expressed in grains):

.4256 / .1064 = 4

Keeping in mind there is a lot of "about" and "approximately" and "give or take". The reasoning is that powder VMD is held a constant from the manufacturers plus or minus a percentage. Something like 15% or 18%, I really don't know.

Ron

Stats Shooter · April 3, 2017, 02:36 PM

Nicely done Ron on the volume conversion.

Like you said/showed, we measure powder by weight but pressure changes with volume. So two completely different units of measure. However, at most guy's reloading benches, we simply do not have the equipment to truly measure the volume of a cartridge. But we can easily and accurately measure weight down to the 1/10 of a grain (usually).

And like you said, we can use a liquid which will fill every single nook and cranny of a case, measure its weight, and then use a conversion calculator to approximate what that represents in volume.

However, getting the exact number of cc's that the case varies by or how much powder that equates to is not actually necessary. We know that a SAAMI .300wm average 90.4 gr of water. We also know that a Norma .300 win mag case on average holds 95.5 gr water (verified by me personally). And finally I know that a Remmington .300 wm case holds approx 88 gr water (also verified by me).

So I know that a piece of Norma brass holds about 8% more water than a piece of Remmington brass in .300wm. Which you can approximate as volume. And IF you hold all other variables equal such as powder brand/lot/burn rate, bullet and seating depth, primer ect, then you know you could likely fit more powder in a piece of Norma brass than Remington AND pressure would be lower at the SAME powder charge in the Norma brass.

Now, being able to do what quickload does in attempting to estimate velocity, pressure etc would require some very exact conversions and quite a bit more accurate measurements than I am capable of.

But what I can definitely say is, a load developed in Norma brass will need to be completely re-worked in Remington brass or Winchester....or that mixed headstamp batches in the .300wm would be a bad idea.

That is all i attempted to say, nothing more.

RC20 · April 3, 2017, 05:13 PM

I am going to offer a simplistic approach.

I do want to agree complete with Mississippi that you have to keep an eye on things as it can go South.

I started out with the old "Military Brass holds less and you need to drop a grain.

So as I was shooting 30-06 I weight cases I wanted to see.

I contend as the external dimensions are very close, if there is a weight difference it has to be volume.

FC was the heaviest weight at 205 avg

RP was next at around 195

I also had some Hornady, Winchester, HXP and other odds and end.

PPU has proven to be analog to RP. Lapua I forget, someplace close.

All were less than RP. Norma being some of the lightest as was Hornady. Down around 180 as I recall.

Hmmm. Any military I had was less than RP, I don't say its universal but that sort of knocked the Military brass automatically needs less powder, FC does

Mississippi's is data seems to confirm, the variations I have seen were more new cartridges, older stuff has followed the FC, RP relationship (like RP).

So, what does it mean?

So with new brass I just weight some cases.

I don't water them, I just weigh them which is easy and another major benefit to the electronic scales.

I tend to use RP as a reference as its what I shoot 308 and 30-06 in mostly and its long established and seems to be consistent .

I know people will disagree with me, but case weight has a correlation to volume, they are not adding lead to the brass so the mixes and weight are going to be roughly coupled with volume.

Load a case that weight more than what you have and back off a couple of grains. Big un like the 300 WM, maybe even 3.

Frankly the biggest issue as we are all careful (right?) is the case volume messes with the pressure a bit and our SDs go out of line changing where we hit.

As I want to hit one hole, that is important to me (as I will never hit better than 1/4 I don't go to nth degrees. )

Anyway, new brass, weight it, see how it compares.

I think a bullet and squashing water out is iffy, we don't all seat the same depth and there can be a lot of variations there.

Not sure how you do minuses free water either.

Unclenicks details on water to case volume is good as it puts it in perspective.

But I don't think it has to get too complicated.

Weight your new cases see if there is a difference and be ready to adjust if needed).

You may hold and sneak up on that ideal charge again if they are larger.

You may drop a couple of grains and see.

Either way you should be safe with at the very worst a bit of pressure.

A bit is not what we want, but we almost all nudge it from time to time

What we don't want is a LOT of extras pressure.

April 1, 2017, 03:39 PM	#52
Nvreloader Member Join Date: January 13, 2017 Location: Western NV Posts: 48	Reload Ron Glad I could help, in a small way. Tia, Don __________________ "Any person that fears me owning a firearm, then I have reason to fear that person" NRA Life Member Nam "Oct 67-Dec 68", 173rd ABN 2/503rd "Recon"

April 1, 2017, 09:39 PM	#54
Stats Shooter Senior Member Join Date: August 26, 2016 Location: North Dakota Posts: 1,636	No Don, You were correct the first time. The volume, as in how much water I can fill a .300 win mag case with, can vary by 8 graines from brand to brand. Last edited by Stats Shooter; April 1, 2017 at 11:48 PM.

April 3, 2017, 09:57 AM	#55
Unclenick Staff Join Date: March 4, 2005 Location: Ohio Posts: 21,063	Yes. It seems only to be true in .300 WM, but case water capacity is measured in grains of water weight in this country, and those are the grains being referred to. If a case is made from 72:28 brass, like Norma's, the case weight difference should be about 68 grains if exterior dimensions match exactly. I've got .308 cases that are almost 40 grains different, so that is not an unimaginable number in the larger case. __________________ Gunsite Orange Hat Family Member CMP Certified GSM Master Instructor NRA Certified Rifle Instructor NRA Benefactor Member and Golden Eagle

March 30, 2017, 01:32 PM	#51
Reloadron Senior Member Join Date: June 8, 2016 Location: Cleveland, Ohio Suburbs Posts: 1,750	Don, thanks for the tip. The primer pockets were a PITA to say the least. I started with candle wax which did work but settled on the clay as I could weigh each small ball before using the stuff. Funny you mentioned the lathe. Before I retired I had an entire small prototyping machine shop at my disposal.Unfortunately when I retired I lost access to that stuff. Can't say I miss going to work daily but I sure miss that machine shop and some of the best machinist and mechanical engineers to answer my questions. Those 50 cases are all cleaned and primed. During the next few days powder and bullets and hopefully good weather to shoot. Ron

April 1, 2017, 05:34 PM	#53
Don Fischer Senior Member Join Date: March 2, 2017 Posts: 1,868	Well I figured out where I went wrong. Title say's case capacity! Actually it's the case's themselves that vary as much as 8 grs.

April 3, 2017, 11:51 AM	#56
Reloadron Senior Member Join Date: June 8, 2016 Location: Cleveland, Ohio Suburbs Posts: 1,750	Confusion? I think maybe a little confusion may stem from the units. Grans for example are a unit of weight and like grams are not something we associate with volume. That said we can make a connection in that 1.0 gram of pure water at a given temperature will occupy a volume of 1.0 cc (cubic centimeter). This makes for a convenient path from grains or grams units of weight to a unit of volume. gr = grains g = grams 1.0gr= 0.06479891g 1.0g = 15.4324gr grams x 15.432 = grains grains / 15.432 = grams 1.0g of water = 1.0cc of Volume. So when we say 8.0 grains of water we are actually looking at 8.0 * .0648 = 0.5184cc of volume. How much powder is that? Well, that depends on the powder. All powders have a different VMD (Volume Metered Density). While a pound of lead and a pound of water weigh the same they will have different volumes. This is what the Lee Dippers are based on with the Powder VMD Associated Chart, the density of the powder determining the weight per unit of volume. Example: If a powder has a VMD of .1064 , and the desired charge weight is 4 grains, 4 x .1064 = .4256, or . 43 cc's Charge Weight (grains) * VMD = Volume in cc That formula can be manipulated however we choose to solve for the unknown. If in the above the Volume (expressed in cc) is known and the VMD is known the weight can be calculated (expressed in grains): .4256 / .1064 = 4 Keeping in mind there is a lot of "about" and "approximately" and "give or take". The reasoning is that powder VMD is held a constant from the manufacturers plus or minus a percentage. Something like 15% or 18%, I really don't know. Ron

April 3, 2017, 02:36 PM	#57
Stats Shooter Senior Member Join Date: August 26, 2016 Location: North Dakota Posts: 1,636	Nicely done Ron on the volume conversion. Like you said/showed, we measure powder by weight but pressure changes with volume. So two completely different units of measure. However, at most guy's reloading benches, we simply do not have the equipment to truly measure the volume of a cartridge. But we can easily and accurately measure weight down to the 1/10 of a grain (usually). And like you said, we can use a liquid which will fill every single nook and cranny of a case, measure its weight, and then use a conversion calculator to approximate what that represents in volume. However, getting the exact number of cc's that the case varies by or how much powder that equates to is not actually necessary. We know that a SAAMI .300wm average 90.4 gr of water. We also know that a Norma .300 win mag case on average holds 95.5 gr water (verified by me personally). And finally I know that a Remmington .300 wm case holds approx 88 gr water (also verified by me). So I know that a piece of Norma brass holds about 8% more water than a piece of Remmington brass in .300wm. Which you can approximate as volume. And IF you hold all other variables equal such as powder brand/lot/burn rate, bullet and seating depth, primer ect, then you know you could likely fit more powder in a piece of Norma brass than Remington AND pressure would be lower at the SAME powder charge in the Norma brass. Now, being able to do what quickload does in attempting to estimate velocity, pressure etc would require some very exact conversions and quite a bit more accurate measurements than I am capable of. But what I can definitely say is, a load developed in Norma brass will need to be completely re-worked in Remington brass or Winchester....or that mixed headstamp batches in the .300wm would be a bad idea. That is all i attempted to say, nothing more.

April 3, 2017, 05:13 PM	#58
RC20 Senior Member Join Date: April 10, 2008 Location: Alaska Posts: 7,014	I am going to offer a simplistic approach. I do want to agree complete with Mississippi that you have to keep an eye on things as it can go South. I started out with the old "Military Brass holds less and you need to drop a grain. So as I was shooting 30-06 I weight cases I wanted to see. I contend as the external dimensions are very close, if there is a weight difference it has to be volume. FC was the heaviest weight at 205 avg RP was next at around 195 I also had some Hornady, Winchester, HXP and other odds and end. PPU has proven to be analog to RP. Lapua I forget, someplace close. All were less than RP. Norma being some of the lightest as was Hornady. Down around 180 as I recall. Hmmm. Any military I had was less than RP, I don't say its universal but that sort of knocked the Military brass automatically needs less powder, FC does Mississippi's is data seems to confirm, the variations I have seen were more new cartridges, older stuff has followed the FC, RP relationship (like RP). So, what does it mean? So with new brass I just weight some cases. I don't water them, I just weigh them which is easy and another major benefit to the electronic scales. I tend to use RP as a reference as its what I shoot 308 and 30-06 in mostly and its long established and seems to be consistent . I know people will disagree with me, but case weight has a correlation to volume, they are not adding lead to the brass so the mixes and weight are going to be roughly coupled with volume. Load a case that weight more than what you have and back off a couple of grains. Big un like the 300 WM, maybe even 3. Frankly the biggest issue as we are all careful (right?) is the case volume messes with the pressure a bit and our SDs go out of line changing where we hit. As I want to hit one hole, that is important to me (as I will never hit better than 1/4 I don't go to nth degrees. ) Anyway, new brass, weight it, see how it compares. I think a bullet and squashing water out is iffy, we don't all seat the same depth and there can be a lot of variations there. Not sure how you do minuses free water either. Unclenicks details on water to case volume is good as it puts it in perspective. But I don't think it has to get too complicated. Weight your new cases see if there is a difference and be ready to adjust if needed). You may hold and sneak up on that ideal charge again if they are larger. You may drop a couple of grains and see. Either way you should be safe with at the very worst a bit of pressure. A bit is not what we want, but we almost all nudge it from time to time What we don't want is a LOT of extras pressure.