Home Forums Hunting & Shooting Ask The Gunwriters Do Brands Matter 2 ?

After weighting samples, I would say mostly No. Three were pretty close, 182 to 188 for PPU,FC, and R-P. Hornady on the other hand was 170 to 172. These were 270 range brass that were formed and trimmed to 6.5-06.

Never understood weight sorting of brass. Measuring and sorting by capacity yes.

downwindtracker2,

In the 1990s I had an accurate Ruger 77 .30-06. At that time there was enough difference in the weight of Remington and Winchester brass that handloads using the 200-grain Nosler Partition in Winchester brass required two more grains powder to get the same velocity (and accuracy) as in Remington brass.

If the cases are all sized the same way, either in the same full length die or fireformed in the same chamber, then trimmed to the same length, you will find a direct correlation between weight and capacity.

It is much faster to sort by weight than capacity.

Well actually not always. After trimming to same length LC, Nosler, Norma 223 and 556 there was as much as 5 grains weight difference but case capacity only varied by 1.5 grains between them.

Exactly how are you measuring case capacity Swifty? I'll ass-u-me that it's grains of water, but it could be grains of powder. If you're doing weight of water, the specific gravity of cartridge brass is 8x that of water. A 1.5 gr difference in water equates to a 12 gr difference in brass.

Okaaaay....Let's do some math, using your results.

A typical .223 Rem case weighs about 95 +/- grains. So a variation of 5 grains with an average weight of 95 grains would get a weight variance of +/- 5.26% .

A typical .223 Rem case holds about 28.8 +/- grains of water. So a variation of 1.5 grains with an average capacity of 28.8 grains would get a capacity variance of +/- 5.21%.

Hmmm......

This

Could it be that brass is dense enough compared to the medium used to measure capacity that the same volumetric change in materials produces a significantly different percentage change of weight for each of the materials?

Thought experiment: Suppose I could add brass material to the inside of a 223 case to double its weight. A change of 100% which would then cause a decrease in capacity. Does the capacity go down 100%? No, it doesn't.

But it will be proportional.

So.

Cases that are sized identically and weigh the same amount will have more consistent internal volumes than cases that aren't sorted by weight. If the outside calculated volume of the case is the same, which it will be, and case A weighs more than case B, then what contributes to the added weight?

The thickness of the brass.

So Case A will have thicker brass, but the same outside calculated volume. Which means the internal volume will be less.

Therefore sorting brass by weight is a legitimate (and time proven by thousands of targets shooters over the decades) way to sort brass for more consistent pressures.

I have seen a big difference in case capacity between 300 win mag Hornady brass and Norma brass. Enough that there was a 100 fps velocity difference with the same powder charge

To be clear, I was not arguing against your point.

No bud he’s arguing with me. So since I have been trying to find time to correlate the data from 5 firings which will give me an actual statistical base for ES/SD but here goes.

The test load is 24 grains LT32, Speer 52 match with 7 1/2 primers. The test bed is a Cooper 21 223. All rounds were ~.001 BTO seating. Chronograph Oehler 35P. The reason for the test was how much difference between commercial 223 brass and 556 brass but it fits.

I took rounds fired in a AR of Norma and Federal 556. 10 rounds of Norma that were found to be within .5 grains weight and not in need of trimming. After sorting by weight I did rough case capacity calcs. At the same time I took 10 rounds of various by weight Norma and federal 556 that also didn’t need trimmed ran the calcs on those also.

So on the second firing this is what I came up with.

Norma 556



As you can see weight is within .5 grains and case capacity is within .5 grains.

Next is random case weights ~8 grains. Case capacity ~7 grains.



Now if you notice the variable weight cases shot within 4 FPS of the weight sorted. Also notice they had a much better ES/SD than the weight sorted. 😳
Must note though case capacity was pretty much a wash. This trend on subsequent firing has held up. The ones that started as random weights still out perform the weight sorted. Not by much but it’s there.

That is interesting.

Look at the extreme spread. Would you be willing to take that load to any distance...

Years ago I found that 10 grains difference in case weight equals 1 grain of powder capacity. Roughly speaking of course. I do not use water as a propellant so I don't use that. I also believe it makes more difference with max loads using a full case than say a 10% reduced load with a faster burning powder. Speaking of .473 and .532 head sized cases.

Very interesting dialogue. I'm taking notes and trying to learn. Thanks