Head expansion indicating pressure.....

[fatelvis]

In my effort to drive my 222 bullets "a little bit faster", to minimize wind deflection during 300 yd F-class, I noticed that my once fired Lapua brass is difficult to slide into my hand priming shellholder and my press's shellholder. Even though the loads were under max @ 49,000psi, (according to several manuals and Quickload), they were pretty hot, and I assume this means these cases are now trash.
My questions to all of you are:
1) Is using the shellholder fit an accurate indicator of over-pressure loads?
2) If the max pressure for 222 Rem is 53,664psi (according to Quickload), at what pressure will the case become "deformed", essentially ruining the case for future accuracy?
As usual, thanks for your experience and wisdom Guys!

 

[jpretle]

If they fit easily before and now are an 'interference fit', I would say your brass has expanded. Are your primer pockets still tight, or does the primer go in w/ less resistance than the first time??
You can find a great dissertation on how to measure case head expansion, in a book written by Bob Hagel. The title is "Guns, Loads and Hunting Tips".

 

[fatelvis]

Yes, the cases did fit the shellholders without resistance before. The primers didn't seem to seat any easier.

 

[Jennb]

Did you FL size your brass after firing?

 

[jds holler]

It's possible that you've got a shell holder that is on the tight side of the spec tolerance. I've run into those.

Your problem might not be that bad if primer pockets aren't blown. jd

 

[retired]

yeahhhhhh
if they no longer fit the shell holder, and they did before,
i think your belief in 49kpsi is all wrong.
my guess is you are over,
if you want to go faster, ackley improved, 222 mag, 223

 

[fatelvis]

Did you FL size your brass after firing?

Yes, I did FL resize and bumped the shoulder .001".

 

[Bart B.]

SAAMI max average pressure spec for the 222 Rem is 50,000 psi.

Do not expect any load you use that matches entries into Quickload to give their calculated pressure because you are not using their barrel, reloaded round specs and component lot numbers. A 5% to 10% or greater difference is possible.

Measuring case head expansion amount will vary across the brass qualities for a given load.

 

[Jennb]

Sounds like something went wrong. We shoot a 223 very hard and fast. Never had this kind of issue.

If you not getting hard bolt lift, blown primers or any of the other pressure sign I would say something else is wrong. Just my opinion!

 

[alinwa]

In my effort to drive my 222 bullets "a little bit faster", to minimize wind deflection during 300 yd F-class, I noticed that my once fired Lapua brass is difficult to slide into my hand priming shellholder and my press's shellholder. Even though the loads were under max @ 49,000psi, (according to several manuals and Quickload), they were pretty hot, and I assume this means these cases are now trash.
My questions to all of you are:
1) Is using the shellholder fit an accurate indicator of over-pressure loads?
2) If the max pressure for 222 Rem is 53,664psi (according to Quickload), at what pressure will the case become "deformed", essentially ruining the case for future accuracy?
As usual, thanks for your experience and wisdom Guys!

#1, yes
#2, never, this has nothing to do with accuracy. Cases don't "deform" any differently under this pressure nor does brass "flow" under pressure.

Quite simply, casehead expansion IS the proper way to find max loads for YOUR setup..... the setup being a combination of your case dimensions, your barreled action and your particular brand/lot of brass. Casehead expansion overrides, supersedes, negates, eclipses ANYTHING a reloading program, the experience of your friends or any reloading manual has to say.... casehead expansion is the direct reading, the real deal, the ONLY accurate representation of what's going on.

And quite specifically this is also where the most accurate rifles on the planet operate. BR's and PPC's LIVE here....

The extra velocity won't do you any good as far as bucking wind but it may well be that your most accurate loads live up in this high-pressure area. Generally speaking Bench Rest competition takes place in that narrow window between accuracy and case failure, that point at which the primer pockets actually loosen and start to leak. If you decide to work in this high-pressure node you may well choose to learn about how to get that one, final firing out of your cases before throwing it out....BEFORE you etch your boltface. Getting into the habit of firing primers until they leak will wreck your bolt face over time.

I've got boxes of throw-away varmint ammo loaded with shimmed or glued in primers. Cigarette papers, aluminum foil, Bob-N-Roys primer sealant compound, finger nail polish, JB Weld...

And in 25yrs of running cases up to "leaking primers" I've never etched a bolt face. I've blackened a few, even got a couple with miniscule gas scoring marks visible under a loupe.... but never damaged one.


Fuh'GEDDABout "Copper Units Of Pressure" and sliding cylinders and proof actions, "bomb chambers" and measurements of barrel expansion, strain gages and crush gauges........ in the real world, companies test to casehead expansion.

It's REAL, it's ACCURATE and most importantly it's SAFE.

You've just encountered what may end up being the most important accuracy tool in your tool box.

 

[fatelvis]

If you not getting hard bolt lift, blown primers or any of the other pressure sign I would say something else is wrong. Just my opinion!

Thanks so much for the input guys!
I never experienced hard bolt lift, or cratered primers. But after reading Alinwa’s post, I’m suspecting I may be on the ragged edge of pressure. I know Lapua brass is relatively soft, and may be telegraphing the pressure signs through head growth, without showing signs at the primer or bolt stiffness.
Your thoughts?

 

[Bart B.]

Quite simply, casehead expansion IS the proper way to find max loads for YOUR setup.....

What cartridge brass metallurgy properties are the standard to use? Yield strength, elongation percentage and hardness specs for example. If we don't use the same "ruler," the same psi level in the case won't expand the case equally across all. How is the ruler certified to be accurate to 4 or more decimal places?

The proper way for real psi numbers is a calibrated piezoelectric transducer system. All others are a UWAG. If you've ever shot proof loads, you'll easily understand. If not, you need to as its a good education on estimating peak pressures.

 

[mikecr]

Not mentioned is your chamber dimension/fit near webs.
If your brass is simply yielding at the breech, with normal loads, then there is either poor breech support or lack of case support due to excess clearances, or both.
And I doubt this is lacking breech support in 22cal.

 

[Bart B.]

Fuh'GEDDABout "Copper Units Of Pressure" and sliding cylinders and proof actions, "bomb chambers" and measurements of barrel expansion, strain gages and crush gauges........ in the real world, companies test to casehead expansion.

That takes the cake from every bakery on earth.

Why was the lady at Lake City arsenal loading 7.62 NATO ammo in a transducer equipped test barrel reading a psi number on the display as I watched her do that last October? Same thing two years earlier at the Hornady plant in Grand Island?

Why are certified proof loads from ammo companies certified to produce a given psi number in an industry spec test barrel instead of any case dimension change?

Why doesn't SAAMI cover case expansion and list standards and specs instead of copper crusher and piezoelectric transducer ones?

Sorry, but that's absurd.

 

[pirate ammo]

would if the case is not fully in the chamber but out just a wee bit,,whats going to happen,,I'm asking because I'm not sure,,help me Bart,,

 

[Bart B.]

would if the case is not fully in the chamber but out just a wee bit,,whats going to happen,,I'm asking because I'm not sure,,help me Bart,,

Cases are full into chambers when fired. The firing pin spring makes that happen while the pin is putting 25 to 30 pounds of force on it's back end..

Don't anyone dare say cases are held against bolt faces while firing....... ........ ....... I'll have your Mommy take you out behind the wood shed..... . . . . . . ...

The back 2/10ths inch or more of the case is unsupported around it when fired. Everywhere behind the pressure ring to the rim has some thousandths or more clearance to the bolt and barrel. Lots more in the extractor groove.

 

[retired]

drop a case in your chamber and look how much case is sticking out.
i do not have a drawing in front of me, but around .2....and all that brass is thick.
if you expand at the extractor groove you are in the wrong load.
and you need a very good blade mic to measure it well

 

[pirate ammo]

The back 2/10ths inch or more of the case is unsupported

but around .2....and all that brass is thick

I thank the both of you,,

 

[Bart B.]

Copper crushers used in CUP systems have a tarage table supplied with each lot, it has a table listing crushed dimension in .0005" steps and the units of pressure for each dimension.

Nobody does that for cases.

 

[butchlambert]

This is what happens when you ask a question on a forum. Whom do you believe?