Understanding cartridge efficiency

[Elk Hunter 338]

A lot of these guys are simply comparing apples and grapefruit... They wind up their sharp shouldered wonder boomer until the primer pockets start to fail and decry victory as the thing ejected without welding to the bolt. The higher taper shallower shouldered cartridges can't be loaded quite as hot before they get sticky ejection so they'll not ever be run as hard by someone who has ever heard of the "shoe" test.
Modern brass has given us the ability to go quite a bit over the normal 65Kpsi top end without killing brass so what some think of as more efficient is really just more tolerant of overloading.

 

[antelopedundee]

Are you referring to efficiency or quality of cartridges? I've never heard of the efficiency issue in cartridges of the same caliber. However; the better quality cartridges tend to perform better. i.e; .340 caliber comparing Star to Weatherby cartridges; which would you choose? For this caliber I will only use Nosler, Norma, or most preferred Weatherby. The latter usually run $0.15 - $0.20 higher per cartridge. I constantly search reloading sites to find them around $2.00 / cartridge.

The OP's premise is screwy. 2 cartridges of the same capacity are unlikely to have dis-similar efficiencies unless you go to extremes like the 30-06 vs the 17-06.

 

[Pdvdh]

Best info in this thread is Proof is having quality control problems manufacturing their barrels. Good to know... A common consensus had been that they walked on water. Or rather, liquid nitrogen, due to their super cooling properties.

Didn't even need popcorn to get this noteworthy take home message.

FWIW, I own one Proof carbon fiber manufactured a couple years ago. It seems OK so it must pre-date the current manufacturing issues.

 

[Stiltsville]

The OP's premise is screwy. 2 cartridges of the same capacity are unlikely to have dis-similar efficiencies unless you go to extremes like the 30-06 vs the 17-06.

That is not the issue. The premise touted by every wildcatter is that by changing case shape velocity is improved. It has been proven wrong so many times it's laughable. No AI is faster unless you put more powder in it. Take your AI whatever and use the exact same components as a non AI. It will be slower as the case volume is larger. Just like shooting a 30-30 load in a 30-06.

 

[bigngreen]

That is not the issue. The premise touted by every wildcatter is that by changing case shape velocity is improved. It has been proven wrong so many times it's laughable. No AI is faster unless you put more powder in it. Take your AI whatever and use the exact same components as a non AI. It will be slower as the case volume is larger. Just like shooting a 30-30 load in a 30-06.

So how would you explain two case designs that are exact same capacity and same parent case yet you can't get the same velocities out of the same weights of powder?

 

[Canhunter35]

Thats why I asked what barrel. Proof has been replacing one after another for this very reason!!
Ive had several clients blow primers 3-4 grains under max!
Some aren't bad enough that people even know that there is a problem, they just think they have a slow barrel.
I havent posted about it because I don't like doing that but I guess its time. To their credit, they are replacing MANY barrels!

Is this due to the tight bore issues?

 

[elkaholic]

Is this due to the tight bore issues?

Thats my understanding. Pinched!

 

[antelopedundee]

That is not the issue. The premise touted by every wildcatter is that by changing case shape velocity is improved. It has been proven wrong so many times it's laughable. No AI is faster unless you put more powder in it. Take your AI whatever and use the exact same components as a non AI. It will be slower as the case volume is larger. Just like shooting a 30-30 load in a 30-06.

Changing case shape gets you nowhere as far as increased velocity goes When Ackley "improved" the 6.5-06 he not only changed the shape, but he increased capacity too. The QL shows that the 6.5-06 case holds 60.46 grains of water while the 6.5-06AI case holds 65.53 grains of water. Had he wanted to keep case capacity the same he would have set the shoulder back some. His only option to increase case capacity was to change the shape. This allowed a little extra velocity by using more of the same or a slower powder. His opinion was that maximum efficiency was reached with the parent case. Of course with all of the newer powders the 6.5-06AI has gained a measure of popularity. Had he had them available his conclusion may have been different.

 

[Stiltsville]

There is no such thing. cases with identical capacity, using the same loads will have the same velocity.

Again I'll post this link. Please read it.

Ammo: Does Case Shape Really Matter?

There have been a number of factory and wildcat cartridges that have played with case design. But has it had any real effect on ballistics?

gundigest.com

 

[bigngreen]

There is no such thing. cases with identical capacity, using the same loads will have the same velocity.

Again I'll post this link. Please read it.

Ammo: Does Case Shape Really Matter?

There have been a number of factory and wildcat cartridges that have played with case design. But has it had any real effect on ballistics?

gundigest.com

But they don't, chamber the parent case develop a load rechamber to new other design and set it back a 1/4 inch use the same load and velocity drops, what's at work there then?

 

[Stiltsville]

But they don't, chamber the parent case develop a load rechamber to new other design and set it back a 1/4 inch use the same load and velocity drops, what's at work there then?

Who are "they" ? Link to source ? Did you even bother to read the GD article ?

 

[bigngreen]

Who are "they" ? Link to source ? Did you even bother to read the GD article ?

Yes I read it, multiple times! Again how do you explain the change in velocity dropping from parent to new design case of the same capacity, your the expert, I'm just a country boy with a chronograph and Pressure Trace asking questions!!

 

[Stiltsville]

There is no evidence to confirm your theory. When you can produce it, we'll be listening. Until then it's just internet blather.

 

[bigngreen]

There is no evidence to confirm your theory. When you can produce it, we'll be listening. Until then it's just internet blather.

Surely you can apply yourself more than just repeating gun rag articles!