Understanding cartridge efficiency

[Bart B]

For the 6.5-06 A Square, QuickLoad gives Useable Case Capacity: 60.456 grain H2O = 3.925 cm³ Where would they have gotten that from?

Measuring the case capacity in the one they had? Or some other source? Ask them where it came from.

 

[antelopedundee]

Measuring the case capacity in the one they had? Or some other source? Ask them where it came from.

Was just wondering if there was some official number. If you make a case to the blueprint, wouldn't that work?

 

[Bart B]

Was just wondering if there was some official number. If you make a case to the blueprint, wouldn't that work?

I don't think so because case weight comes into the equasion as this data shows

PPU case volume average 71.23 grains of water, 185.93 grain average empty case weight.

Remington case volume average 69.06 grains of water, 199.63 grain average empty weight.

Federal case volume average 69.46 grains of water, 206.2 grain average empty weight.

Outside dimensions of them are unknown.

You can strip a full length sizing die then run the empty case full into it, fill with water then remove it to weigh water filled case. Difference between full and empty case weight is that of the water.

 

[Lefty7mmstw]

I have tested a couple wildcats and parent cases and multiple powders in each, after a few with doing the work of installing the test equipment, calibrating all the chambering and loading it you'll find it's really a buzz kill to learn pressure signs still show up at the same pressures, you see pressure is only one part of the equation. The most interesting thing actually was watching the reflective pressure signature from different muzzle brakes.

interesting on the muzzle break causing a pressure signature... Ever notice a tight spot in the barrel produce a bit of a pressure spike? I had that issue on my old 7stw when I had a transducer on it. Wondering if that one is a rarity or common...

 

[DJ Fergus]

There is no such thing as cartridge "efficiency" as Handloader proved several years ago with their 300 WSM vs 300 H&H test.

Roy tried to peddle this BS in the 1950s and people fell for it. They still do.

My thoughts also. I really don't buy into the efficiency thing but I won't use my time to argue it.

 

[antelopedundee]

I don't think so because case weight comes into the equasion as this data shows

PPU case volume average 71.23 grains of water, 185.93 grain average empty case weight.

Remington case volume average 69.06 grains of water, 199.63 grain average empty weight.

Federal case volume average 69.46 grains of water, 206.2 grain average empty weight.

Outside dimensions of them are unknown.

You can strip a full length sizing die then run the empty case full into it, fill with water then remove it to weigh water filled case. Difference between full and empty case weight is that of the water.

What QL has is good enough IMO. Was just wondering if there was some sort of standard volume for each cartridge case. I'd be more interested in capacity to the bottom of the neck vs the entire case. I suppose one could just calculate the volume of the neck and subtract that amount out.

 

[antelopedundee]

Efficiency can be looked at simply as getting the same or more from less.

If cartridge A gives 3000 fps mv with 55 grains of powder X and 3000 fps mv with 50 grains of powder Y which one is more efficient?

 

[Swamplord]

So should I call this the 300 Efficiency then ? (sounds like a new super duper washing machine)
based on all the bs about efficiency floating around ..... so then at less than 2" in case length and more capacity than the 300 WSM and velocity with 180 gr - 230 gr bullets matching 300 WBY while fitting in a short action box makes this the most efficient 30 caliber cartridge ever designed

 

[25WSM]

Are you doing 7mm version?
Shep

 

[Bart B]

If a standard volume is desired, first use case outside dimension specs to calculate a weight base using cartridge brass specs. One spec says cartridge case brass weight is .308 pound per cubic inch.

Second, subtract case weight from the base weight to get the case volume's weight if full of brass.

Third, reverse calculate the volume weight to cubic units.

If a mechanical engineer has a better way to establish a standard volume for cartridge cases, three cheers for him.

If the case volume at peak pressure is preferred, use chamber dimension specs

 

[antelopedundee]

If a standard volume is desired, first use case outside dimension specs to calculate a weight base using cartridge brass specs. One spec says cartridge case brass weight is .308 pound per cubic inch.

Second, subtract case weight from the base weight to get the case volume's weight if full of brass.

Third, reverse calculate the volume weight to cubic units.

If a mechanical engineer has a better way to establish a standard volume for cartridge cases, three cheers for him.

If the case volume at peak pressure is preferred, use chamber dimension specs

I don't really care all that much and apparently the folks at SAMMI don't either, but it seems to me that a case manufactured to SAMMI specs should have a standard weight and therefore a standard volume. For the finicky among us a weight/volume matters. For the rest of us not so much. If I took 100 new .25-06 cases from any manufacture I could probably put the same amount of powder for a maximum load into all of them and that's all that matters.

As for efficiency, I don't much care. I subscribe to the advice of using the powder that fills or nearly fills the case as long as it performs accuracy-wise.

 

[Bart B]

Yes, a case manufactured to SAMMI specs should have a standard weight and therefore a standard volume if they thought it was important. But the other variables in the barrel and ammo consumers use would make it meaningless.

SAAMI test barrels with tight specs would have to be used to establish any meaningful presure and velocity standards.

 

[Elk Hunter 338]

Is this due to the tight bore issues?

its always the barrels fault

 

[Canhunter35]

its always the barrels fault

Lol in my case it was the bullets fault but proof told me they had a bunch go would with tight bore and they were replacing them