.223 Brass brand weights - Study

[9MMand223only]

I ran through my various cells of brass cases, and then gathered 10 of each type and wieghed them all, then averaged.

PPU - 97.1 grains
PMC - 91.24
Winchester - 93.68
PSD - 92.06
LC14 - 92.12
WCC10 - 94.40
RP - 90.60
LC08 - 92.74 (good brass, varied very little ~1%)
Hornady - 93
LC13 - 92
Lapua Match shot 2x, not trimmed: 96 (under 1% weight consistency)
Lapua Match new: 96.10 (under 1% weight consistency)
Nosler: 91.2 (consistent weights, under 1%)
TopBrass: 97.60 (varied about 1%)

Heaviest Brass I have is Lapua, PPU, and TopBrass. TopBrass is decieving because that brass is pretty long brand new compared to Lapua. The Lapua is about .020 shorter than the TopBrass, and because of this difference, the weight is probably the same, I will trim some TopBrass and weight later. TopBrass for the money, looks pretty stout.

Nosler is quite consistent weights.

I will fill each with water, and see how much some of these hold later too.

[FrankenMauser]

Interesting.

[higgite]

The broadly accepted "wisdom" that I have lived by is if you check rifle cases for internal capacity, i.e. water weight, do it with fired cases, not sized cases. Reason given is because when max chamber pressure is reached, the brass has already expanded to fill the chamber. Unless, of course, it's a reduced load. ymmv

[Unclenick]

Hartmut Broemel recommends that for QuickLOAD. Any cartridge that runs at peak pressures over about 30,000 psi he says gets more accurate predictions from the as-fired measurement. Also, fireforming tends to make the outside dimensions of the case body (the part holding the powder) more even. However, if you are comparing cases for when the charge weights will begin to be compressed, you need the as-sized volume. If you are comparing them with other shooters whose chambers may not be the exact same size as yours, you generally want to compare them as they come from the factory before firing.

There is a fairly extensive table of brass brands and capacities at the 6mmBR.com/223Rem.html page. Scroll down about 25% of the way and it shows up on the left side, with .223 AI in a second table underneath. There is a list of some brand alloys on this page. The densities of these different alloys can be interpolated from:

From Matweb:

Copper:Zinc / Density at 68°F  (common names)

60:40 / 8.39 gm/cc   (aka, Muntz Metal)

70:30 / 8.53 gm/cc   (aka, Cartridge Brass and 260 brass)

80:20 / 8.67 gm/cc   (aka, Low Brass)

100:0 / 8.93 gm/cc   (aka, Copper)

[9MMand223only]

I am going to do a very revealing test this weekend about case volume VS velocity using the same OAL, and same exact powder charge.

The question I will answer is....

How much more velocity is achieved but having cases with:

28.8 H20 Volume

VERSUS

30.5 H20 Volume cases.

I will post what quickload says, then post the actual results. Should prove entertaining. So much debate about cases out there. Like tons.

Coincidentally, the above test will have accuracy numbers too.

This will be fun.

[higgite]

Looking forward to your results.

[9MMand223only]

I didn't have any cases less than 29.

So I will be testing 29.3 VS 30.0

it was hard to find 5 cases of each exact H20 fill.

And they are trimmed to the exact same OAL as well. the 29.30 is ~ 16k less long as the 30.

[chiefr]

I have weighed many different calibers of brass and noticed not only variation between brands but within brands. R-P seems to have the most variation.

I find this important if related to case volume and compressed loads. Fact is less weight in most cases allows for more powder.

To the contrary is Norma and Lapua. Both brands are far superior and weight differences are minor.

[rude robert]

I tried a few years ago putting water in the 223 cases, I did each one a few times each and never go the the same results. I figured there were air bubbles or something else causing the issue and gave up. Is there a trick to getting one case to give the same water weight? I didn't try any other cases just the 223, I was playing around with 223 and 556 trying to find the real difference

[hartcreek]

Why do you think that you need to know how much water as case will hold?

Once you shoot x,y,z cases through your rifle or run them through your sizer die the external dimensions will be the same so simply weighing them will tell you wich cases would hold more water. All you want to know is which cased are the heaviest so that you work up your loads uning the heaviest cases ie the cases with the smallest volume.

[higgite]

Once you shoot x,y,z cases through your rifle or run them through your sizer die the external dimensions will be the same so simply weighing them will tell you wich cases would hold more water.

Not so. See the links in Unclenick's post #4. My own personal test, admittedly limited in scope, showed the same inconsistent relationship between weight and internal capacity, especially among mixed headstamps and to a lesser degree in the same headstamp. And, yes, I have more time than money.

[Unclenick]

Yes. You not only need them to be the same alloy for weight to predict capacity, you need the dimensions to be identical. You could, for example, have a wider head with a shorter web thickness, have it weigh the same but have greater internal capacity. There are tolerances for that head width and also for rim thickness, extractor groove angle cut, etc. Can all throw you off. The last time I compared 308 Win brass and tried to predict water capacity by weight, I got about a ±20% error spread, but the sample size was small.

On comparing case capacities for effect on cartridges, there is an old rule of thumb published by Wm. C. Davis, Jr. in the 1960's that says for otherwise identical cases, you subtract about one grain of powder for every 16 grains of additional brass weight. In other words, you have to have 1.6 grains of difference for 0.1 grains of powder difference to occur. That's the limit of resolution of most powder scales, so anything less than that isn't likely to be very useful.

In QuickLOAD's model I find 14 to 16 grains of brass weight, or about 0.06 to 0.07 grains of powder per grain of brass weight difference is right when the brass dimensions are fixed. It varies with the bullet weight and powder characteristics a little. However, it's all within Mr. Davis's empirically tested ballpark.

A second issue, if you are looking for effect on velocity, is bullet pull. Bullet pull affects start pressure which affects how fast you hit peak pressure which affects final velocity. If you don't own the RSI Load Force instrument for sorting cartridges by exact seating force, you can try standing on a bathroom scale to see if you can get a useful read, or pulling the press handle with a fish scale.

[9MMand223only]

Unclenick, you are good man. You know a lot.

What you said is exactly my experience. case weight does not have bearing on capacity absolutely, as in my test conclude a similar result to the +/- 15% range of capacity, which in english means case weight does not determine case volume in of itself.

The brass is thinner and thicker in pretty much all brass. The neck thickness has a great deal to do with bullet pull weight. This is part of the reason competition shooters measure the thickness of the neck, then "cut" it on a machine down to a consistent thickness, so all their rounds have as close as possible pull weight. Thats part of the reason, not all of it.

ANd the other poster, I notice the same trend. The R P brass range is all over the place, outside of the "normal" brass 1.5% difference spectrum.

[steve4102]

Here is one example of why case weight is not an accurate indicator of case volume.

These are both 300WSM cases, note the difference in the diameter of the case head.