Case capacity by brand can vary by 8 Graines!!!

I would think that would leave someone wide open to law suits? I know a good number of people that load that don't give a though to mixing case's. If they are doing 300 mag or 308 and they can vary as much as 8grs difference in capacity, how come we don't hear about more blown up guns?
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The main reason we don't hear about lots of lawsuits is that there are still some things in law that make what you do, your own responsibility.

The reason we don't hear about more blown up guns is that most of the time, even extreme pressure variations due to case volume variations don't reach blow up levels. Most of the time.

The fact that brass from different sources varies is a long known thing. Known for as long as there has been brass from different sources. Knowing that loads must be tailored for the components used is a fundamental part of reloading, always has been.
 
This has been very interesting, got me totally confused but I've never got into the physic'a of the case's or bullet's. Different brand of case and I generally start lower than normal. I don't seperate hand gun case's by brand thougt and I don't push max load's and never exceed max loads. In fact I've never gone to a max load even with cast bullet's which is the only stuff I use in handguns anymore.

When this started, I though the difference was even in brands of the same make! I re read this whole post a couple more time's and I see that it's not a difference within the same brads but between different brands.

Great thread!
 
Don Fischer
When this started, I though the difference was even in brands of the same make! I re read this whole post a couple more time's and I see that it's not a difference within the same brads but between different brands.
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That is the key point from the beginning, the variability between case brands. Some sort cases within the same brand/lot by volume to try and get it exact. But my last batch of Norma brass for my .300 win mag only differed by 2 grains in weight, and by 0.1 grains in volume!!! that is pretty darn consistent. In general I do not think you will find wide swings in volume within the same brand/lot of brass, even in the cheaper winchester cases though I have no data to back that statement up.

I also do mixed headstamp batches for plinking around in my AK and carbean length AR's...But those loads are fairly mild since I know that cases can and do vary.
 
I went ahead and worked with the cases I mentioned earlier. The cases showing up in the spread sheet are Remington, Winchester, WCC 10, LC 13 and Federal. All cases were resized so their outside dimensions are the same. All cases were deprimed and trimmed identically. Looking at the chart the only numbers of actual importance would be the lower right and the cases having the lowest Standard Deviation number would be the best. The WCC 10 cases offered the best choice overall. Not that this means much as next week I could perform the same test using different lots and another manufacturer would come out on top.

Here are the numbers:
Case%20Volume.png


The lower right corner reflects actual case volume expressed in cc (Cubic Centimeters or can be expressed as centimeters ^3. So what does it actually mean? To know what it means as to powder you would look at the VMD (Volume Metered Density) of the powder. The Lee VMD Chart can be found here. A good explenation of VMD can be found here.

I used .308 Winchester simply because I have more of it than much else laying around.

Ron
 
Nice Work Ron.

And while you said yourself, things can change some from lot to lot, your experiment passed the "sanity" test off the bat as you found less volume in military cases than commercial...which is well known and documented. Also, it shows which batch/brand is most consistent. Like you said it looks like WCC and also Federal are pretty consistent. Im a bit surprised LC has almost a 2 grain extreme spread, but there of course could be some measurement error.

But your work does reinforce the point made, that you need to adjust your load if you switch brands....or if you are doing a mixed head-stamp batch, stay mild on the charge, because if you work it up near the max in Winchester brass, and there are some WCC cases in there, you may wind up having to pound them out with a hammer!
 
Mississippi, thank you. Now I just need to remove the clay from the primer pockets and cook out the remaining moisture. :) Then I'll load them all with the same powder charges and bullets. Sooner or later sunshine will return to NE Ohio and I will see how we do at the range and over the chronograph. They will be run through my bolt gun as it delivers the best. Yeah, looking at weight versus volume and all things considered it is interesting.

Like I mentioned. Next week I could do it all again using different lots and likely have different results. I do have some brand new Lapua I omitted. :)

Ron
 
Don,

Both the Lake City plant and, when it was still a military facility, Frankford Arsenal made their own brass. Today, though, if you look at Natchez and others selling new, never-loaded brass with military headstamps, you see things like "Federal Lake City brass", meaning Federal made it on contract with the LC headstamp, probably for loading at Lake City, though that's just a guess. In my view they should not introduce that confusion. It should be labeled FC for Fedearal Cartridge instead of LC, then the box should say "loaded at Lake City facility" if that is what is happening.

The NATO STANAG standards are much more specific about brass than SAAMI is. SAAMI has brass outside dimensions and primer pocket and primer dimensional standards. The NATO STANAG drawings go on to give case head internal thickness from base to floor, wall thickness at two locations, inside head radius and, in the attached drawing are small x's to indicate where hardness tests are to be done on a sectioned sample. The one thing they don't indicate is the primer pocket dimensions. That is because some members will use Berdan priming.

See the attached drawing.

Once the ATK redesigns are accepted, all this may change and I won't be surprised to see some of it dropped to make things easier on the commercial manufacturers. We'll have to see.
 

Attachments

Unclenick, yes I hear you. I have always wondered about the brass sold new as unused GI brass. I figured it was whoever was running the arsenal under contract. The brass I used was once fired (as far as I know) brass I bought from Brass Bombers. It also has the NATO symbol on the cases. Actually the WCC stuff has shot really well for me, and I have been pleased with that stuff. :)

I dried the cases out and I guess I'll use AA 2495 as that has worked well in my .308 Win bolt gun. I have a bunch of Sierra 150 grain Match Kings so I'll use some of those. What I would like is a nice few days up here in NE Ohio allowing the range I shoot at to dry out a little. While I can't measure the pressure I can chronograph the loads and see how they group, assuming I do my part.

Thanks for sharing the standardization drawing. Standardization, another good thing. :)

Ron
 
Reloadron

You might want to try this method for using cases,
when finding the H2o case capacity's.

If you have a lathe or access to one,
get some Teflon bar stock around the 5/8" diameter,
turn down a section to the .175" and .210" diameters,
with the length to fit each size of primers,
make it a snug slide in fit

You can then insert the Teflon base with the correct primer size,
into the primer hole, then fill the case to weigh etc,
less hassle than using clay.

With the larger base makes the case stand up better ,
without tipping over etc.

Reusable for lots of cases etc. :D

Also great info you posted.

Nick,
Thanks for the great info.

Tia,
Don
 
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
 
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.
 
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.
 
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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.
 
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
 
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.
 
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.
 
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