6.5 x 47 Lapua

[alinwa]

BTW, what you're striving for in the reloading game is to get your setup dialed in until you can reload a case 20...50........even 100 or more times without a case failure. I do this with a wide range of cases from 220R up to and including a blown out 338L.


Easier said than done.


UNDERSTAND "incipient casehead separation!"



al

 

[John Kielly]

al,

Maybe you missed one possibility, or needed a bit more explaining.

A case might continue to be used in some circumstances when it loosens up if a larger diameter primer of suitable performance is available.

Did I qualify enough?

John

 

[alinwa]

al,

Maybe you missed one possibility, or needed a bit more explaining.

A case might continue to be used in some circumstances when it loosens up if a larger diameter primer of suitable performance is available.

Did I qualify enough?

John

I've heard of this, never actually experienced it

There was a time when folks were claiming certain Federal offerings were wider. Also CCI's....

But I can't confirm it from my experience.

al

 

[R.DesJardin]

al,

Maybe you missed one possibility, or needed a bit more explaining.

A case might continue to be used in some circumstances when it loosens up if a larger diameter primer of suitable performance is available.

Did I qualify enough?

John

You've stretched the case past it's yield point and I wouldn't want to reuse it. Brass work hardens very easily then become brittle as does many metals. I've seen mild steel do this also, worked hardened and become so brittle it fractures.

 

[mks]

You've stretched the case past it's yield point and I wouldn't want to reuse it. Brass work hardens very easily then become brittle as does many metals. I've seen mild steel do this also, worked hardened and become so brittle it fractures.

We stretch the neck of the case past its yield point with every firing, and with every resizing. Unless there is some other problem, we can go past yield hundreds (thousands?) of times without failure. Steel has failure stress close to yield stress after work hardening. Brass doesn't. There is no reason to worry about case heads getting brittle and cracking under normal circumstances.

Excessive shoulder setback is an exception. In this case, the brass goes WAY past yield and the case head pulls off the body.

Cheers,
Keith

 

[R.DesJardin]

We stretch the neck of the case past its yield point with every firing, and with every resizing. Unless there is some other problem, we can go past yield hundreds (thousands?) of times without failure. Steel has failure stress close to yield stress after work hardening. Brass doesn't. There is no reason to worry about case heads getting brittle and cracking under normal circumstances.

Excessive shoulder setback is an exception. In this case, the brass goes WAY past yield and the case head pulls off the body.

Cheers,
Keith

Sure maybe he can buy some primer bushings since the case is still good.

 

[alinwa]

We stretch the neck of the case past its yield point with every firing, and with every resizing. Unless there is some other problem, we can go past yield hundreds (thousands?) of times without failure. Steel has failure stress close to yield stress after work hardening. Brass doesn't. There is no reason to worry about case heads getting brittle and cracking under normal circumstances.

Excessive shoulder setback is an exception. In this case, the brass goes WAY past yield and the case head pulls off the body.

Cheers,
Keith

Not to quibble but I fail to see a connection here...... casehead separation is not the result of brass being stretched or distorted and then put back, like the neck or the casebody. It's the result of repeated stretching to the point of separation. Head separation is a one way street.

al

 

[mks]

Not to quibble but I fail to see a connection here...... casehead separation is not the result of brass being stretched or distorted and then put back, like the neck or the casebody. It's the result of repeated stretching to the point of separation. Head separation is a one way street.

al

My point is that brass doesn't get brittle like steel. Brass is a ductile material. See the plot on page 3: http://people.virginia.edu/~lz2n/mse209/Chapter8.pdf Casehead failure is ductile.

The web above the casehead does thin before it fails. But it thickens some during sizing. So there is some back and forth on that, ultimately, one way street, which makes it similar to sizing necks. Necks stretched excessively in a large chamber fail by the same mechanism.

Just another observation: Thin spots in the web concentrate the stresses, and these areas thin faster. We spend a lot of time turning necks to make them uniform thickness, which uniforms the stresses. But not many machine the body, or even inspect for uniform bodies.

Cheers,
Keith

 

[alinwa]

My point is that brass doesn't get brittle like steel. Brass is a ductile material. See the plot on page 3: http://people.virginia.edu/~lz2n/mse209/Chapter8.pdf Casehead failure is ductile.

The web above the casehead does thin before it fails. But it thickens some during sizing. So there is some back and forth on that, ultimately, one way street, which makes it similar to sizing necks. Necks stretched excessively in a large chamber fail by the same mechanism.

Just another observation: Thin spots in the web concentrate the stresses, and these areas thin faster. We spend a lot of time turning necks to make them uniform thickness, which uniforms the stresses. But not many machine the body, or even inspect for uniform bodies.

Cheers,
Keith

No.

Simply, no.....

You're misunderstanding the mechanism of casehead separation.

The web above the casehead thins because the brass keeps pulling away from it due to improper sizing. It does NOT go "back and forth like the neck" in fact it will never thin at all if one's dies are properly matched. I can and do resize cases untill they wear out from other things, like the flashholes burn out, and show ZERO thinning at the casehead.

Casehead separation is quite simply a function of improper sizing and can easily be avoided in it's entirety.

The mechanism is this: an improper setup first sets the shoulder back too far, then the force of the firing pin drives the case forward opening a space between the casehead and the boltface, the case expands and LOCKS IN PLACE in the chamber and the casehead is driven back to the boltface by internal pressure.

Do this enough times and the casehead simply pulls off the case....... no "back and forth."

Bottom line, IF YOU'RE TRIMMING YOUR NECKS, you will get a casehead separation sooner or later.


Interestingly enough it takes quite a bit of pressure to stretch the cases on new brass........... I'ma' SWAG around 50,000psi....... Many loads are low enough pressure that the casehead never goes back to the boltface, the gap stays there and the primer "pops up" above the casehead. You _could_ fire most factory 30-06 loads using a hammer and nail simply holding the nekkid barrel in your hand and the case wouldn't leave the barrel!




Nor would the case ever suffer a casehead separation.


Brass more than 30yrs old will sometimes break because it's embrittled by age, but this is again, a different problem.


al.

 

[mks]

You _could_ fire most factory 30-06 loads using a hammer and nail simply holding the nekkid barrel in your hand and the case wouldn't leave the barrel!

PLEASE don't try this. Whether you do back-of-the-envelope calculations or full-blown computer simulations (see http://www.varmintal.com/a243z.htm), the web deforms plastically. Even with the minimum bolt thrust from Al's simulations of 4 ksi, the stress in a 0.030" case wall is 96 ksi, which exceeds the tensile strength of all but hardest of hardened brass.

 

[alinwa]

PLEASE don't try this. Whether you do back-of-the-envelope calculations or full-blown computer simulations (see http://www.varmintal.com/a243z.htm), the web deforms plastically. Even with the minimum bolt thrust from Al's simulations of 4 ksi, the stress in a 0.030" case wall is 96 ksi, which exceeds the tensile strength of all but hardest of hardened brass.

Parker Ackley did it He removed the locking lug from a 94Win and fired it with only his fingers holding it shut.

But then P.O. was a doer, not a simulator.... he practiced what he preached.

I'm not advocating unsafe behaviour I'm simply illustrating that most middle-of-the-road setups have very little bolt thrust. Regardless what the numbers (or computer simulations) say once one becomes aware of the phenomenon it becomes almost second nature to check for popped up primers, they're quite common.

al

 

[alinwa]

Incidentally, Varmint Al's computer predictions show catastrophic gasket failure at pressures well below where BR is practiced....... like in real life 95% of the cases on the firing line SHOULD BLOW OUT, simply cannot be working according to his simulations.

I've argued with him about this very subject here on this very board he's the only guy I know who'll argue with fact. He told me that the typical BR setup "could not work" because the brass cases couldn't contain the pressure...


"But"..... I said....... "they do!"


I've got guns that run at 30,000psi over "catastrophic failure." For dozens, even hundreds of reloads/case.

 

[mks]

Parker Ackley did it He removed the locking lug from a 94Win and fired it with only his fingers holding it shut.

For a 30-30. You can bet he never did it with a 30-06. The cross sectional area of the case is 24% larger and the SAAMI pressure is 43% larger, for (ball park) 77% greater stress in the brass.

 

[alinwa]

For a 30-30. You can bet he never did it with a 30-06. The cross sectional area of the case is 24% larger and the SAAMI pressure is 43% larger, for (ball park) 77% greater stress in the brass.

True, but talk to any Palma guy about spent cartridges "rocking on the primer."

I typically start working up loads such that my "starting loads" aren't capable of stretching the case..... somewhere in the workup the cases begin to give, and my typical working pressure ends up well above the pressure required to rip the case apart. ANY case...... I just run the tough ones hotter. Generally my loading/shooting is accomplished within the top percentile, near unto case failure but I don't accept anything less than 15 reloads/case for hunting rifles, 50+ for target stuff.

And while I've blown off caseheads back in the day, I will never again.

al

 

[mks]

True, but talk to any Palma guy about spent cartridges "rocking on the primer."

If you are saying that the raised primers are evidence that the casehead never touched the bolt, that is not true. For a typical high pressure load, as chamber pressure rises, the primer is pushed out to the bolt face first. Then as pressure rises higher, the casehead is pushed out to the bolt face. The primer slides back into the pocket as this happens. As pressure decreases, the casehead recedes away from the bolt face first, minus any plastic deformation. There still being some remaining pressure, the primer remains in contact with the boltface as the casehead recedes, until the pressure decreases below the level required to overcome the friction between the primer and the primer pocket. After all is said and done, the primer extends beyond the casehead, even though it didn't at the peak of the pressure pulse. You can see this occurring in VarmintAl's animations.

Cheers,
Keith

 

[alinwa]

If you are saying that the raised primers are evidence that the casehead never touched the bolt, that is not true. For a typical high pressure load, as chamber pressure rises, the primer is pushed out to the bolt face first. Then as pressure rises higher, the casehead is pushed out to the bolt face. The primer slides back into the pocket as this happens. As pressure decreases, the casehead recedes away from the bolt face first, minus any plastic deformation. There still being some remaining pressure, the primer remains in contact with the boltface as the casehead recedes, until the pressure decreases below the level required to overcome the friction between the primer and the primer pocket. After all is said and done, the primer extends beyond the casehead, even though it didn't at the peak of the pressure pulse. You can see this occurring in VarmintAl's animations.

Cheers,
Keith

Ummmm, no.

This is the problem with Varmint Al and his cartoon guesses. Some of his assumptions are just WRONG You can perty much make a simulation "show" anything.... it's called GIGO or "make a piss-poor assumption, get a piss-poor result"...... In the real world primers vary in their protrusion with some of them popping up 3-4thou, FAR BEYOND the springback of the brass, which in any case couldn't exceed a thou. (Really, caseheads don't spring back at all but we'll leave that be for now)


Even testing is a slippery slope, let alone this silly "simulation" garbage.....Don't get me started on the "tests" where weighted brass, copper and gilding metal sheets were dragged over surfaces to "simulate conditions inside the chamber." in an attempt to disprove the FACT that cases stick. A fact easily proven using solid testing methods.

This is FACT, primers often pop up several thousandths....

This is also FACT, under normal conditions, cases stick.....

And it's FACT that if you stretch a case or any tube of brass 3-4thou longitudinally over a distance of 15-30thou IT AIN'T SPRINGING BACK!

Now, you show me a mechanism for driving that silly phallic casehead story and I'll TEST IT...... if in FACT them pumped up caseheads will turtle back several thou whilst the poor primer repokes (a goofy contention but one easily tested for ) then you show the driver, you give a step by step replay of the forces acting to effect this and we can make a movie.


BTW....... how does VA account for the FACT that it's common for primers to pop up and then, when the web yields, for the casehead to be driven back FLATTENING THE PRIMER instead of re-seating it? This is commonly cited as an illustration of why using "flattened primers" as an indicator of pressure is problematic.

al-NOTanengineer-inwa

 

[MikeTheRock]

???

But silly people, slobbering chambers into rifle using "Go Gauges" have managed to bugger up enough rifles that a large segment of the competitive shooting population believes the 6X47L to be somehow "less accurate" than the Dasher....

Hi Alinwa,

I've been following this thread a bit as I'm having a 6.5x47 built and I was wondering if you could elaborate on the above quote a bit.

Also, you stated that "...it will never thin at all if one's dies are properly matched." What is your method for making sure ones dies are properly matched?

Thanks in advance,

Mike

 

[alinwa]

Hi Alinwa,

I've been following this thread a bit as I'm having a 6.5x47 built and I was wondering if you could elaborate on the above quote a bit.

Also, you stated that "...it will never thin at all if one's dies are properly matched." What is your method for making sure ones dies are properly matched?

Thanks in advance,

Mike

The easiest way is to get a neck sizing setup ALA Wilson hand dies.....I most often just cobble something up these days because I can..... but you must do what you can to be able to reload some cases over and over without sizing. This is most often called "shooting "neck size only"" So you fire three cases over and over using moderately stiff loads and they will get progressively tighter and tighter. KEEP YOUR LUGS GREASED!!! At some point they'll become uncomfortably tight, like you have to use your palm to close the bolt. Put them into a ziplock.

Now fire some more cases until they're "moderately tight," like you have to use your thumb to close the bolt.

Now fire some more and stop when they're "perfect, just a little feel."


Send the six cases off to Neil Jones ( http://neiljones.com/ ) with a detailed explanation and you'll get back a die which will allow you to wear out a barrel using 20 cases......


Now, there are a host of other issues. For instance most chambers are too small, too tight and will develop a "click" at some point. Your fitted die won't fix this. But it WILL allow you to fire your cases over and over once you figure out how to use it.


If this works, here's a picture from another thread from years ago (YAYYY! Wilbur fixed the 'search' function!!!) which shows some cases that have been fired almost 50 times....

http://benchrest.com/showthread.php?58805-Al-s-6x47L

If the link doesn't go to pictures try scrolling around to find some snapshots

If NOT...... I tried

hth


al

 

[alinwa]

Wow....


I just reread some of that old thread. A lot has changed since then, I was just testing a lot of the stuff mentioned. At the time of that thread the brass was pretty newly arrived in America. I bought from the first three shipments and still have lots of cases. But all of the assertions and testing have proven out.

 

[mks]

This is the problem with Varmint Al and his cartoon guesses. Some of his assumptions are just WRONG

Which ones?

In the real world primers vary in their protrusion with some of them popping up 3-4thou, FAR BEYOND the springback of the brass, which in any case couldn't exceed a thou.

Everything deflects and springs back - the barrel, action, bolt and brass. The final primer protrusion is the product of all of these.

(Really, caseheads don't spring back at all but we'll leave that be for now)

Are you saying that the brass in the casehead somehow violates the laws of physics?

Now, you show me a mechanism for driving that silly phallic casehead story and I'll TEST IT...... if in FACT them pumped up caseheads will turtle back several thou whilst the poor primer repokes (a goofy contention but one easily tested for ) then you show the driver, you give a step by step replay of the forces acting to effect this and we can make a movie.

The movie is already available on VarmintAl. I tried to explain the step-by-step in my last post. It boils down to the pressure late in the pressure pulse being sufficient to push the primer back out, even as the casehead is springing back. It makes sense, because if low pressure pops the primer out before the case head moves, then surely it can do the same thing after the casehead springs back.

As for experiments, one could use plastigage. If it gets squashed thinner than the final primer protrusion, then the primer must be getting pushed out again after the maximum case head deflection.

BTW....... how does VA account for the FACT that it's common for primers to pop up and then, when the web yields, for the casehead to be driven back FLATTENING THE PRIMER instead of re-seating it? This is commonly cited as an illustration of why using "flattened primers" as an indicator of pressure is problematic.

Watch the movie. It's easy to see that the corner of the primer is an area of stress concentration, which leads to flattening, particularly when the case head is driven outward after the primer. The effect is exaggerated in the right hand movie.