223 vs 222m SAAMI presures

[bheadboy]

interesting discovery, the SAAMi 223 psi is 55,000 normal chambers, and higher for those with longer throats

the 222m is 50,000 cup with a SAAMI chamber

if the formula PSI = -17,902 + 1.516 x cup is used the 222m psi relates to 57,898 and if the statistical R/2 is use of 92.8% the result is 53,729 psi at the extreme variation.

I have found no loads by powder providers that reach these levels or come close

something to think about.

I await your critical observation and possibly other comments. Catshooter, Alf?

Bob

 

[CatShooter]

interesting discovery, the SAAMi 223 psi is 55,000 normal chambers, and higher for those with longer throats

the 222m is 50,000 cup with a SAAMI chamber

if the formula PSI = -17,902 + 1.516 x cup is used the 222m psi relates to 57,898 and if the statistical R/2 is use of 92.8% the result is 53,729 psi at the extreme variation.

I have found no loads by powder providers that reach these levels or come close

something to think about.

I await your critical observation and possibly other comments. Catshooter, Alf?

Bob

The 222 Magnum is one of my all time favorites.

First - there is no accurate formula to convert CUP to PSI.

Current Maximum Average Pressure (MAP) for the 223 and 222 Magnum is 55,000 PSI (for BOTH of them) and current MAP for the .221 FurBall is 60,000 PSI. Current MAP for the standard 222 is 50,000.

But the cartridges are all capable of the same pressures - SAAMI sets MAPs based on the firearms that were/are chambered for - and the 222 Rem came out long ago, and was chambered some whimpy-assed rifles like the 340 Savage (with one tiny whimpy lug), and many years ago, Anschutz made a 222 Rem with no lung (a up-graded 22 rimfire action)... so the cartridge was set lower than the others - it used to be 45,000 PSI, so thing are getting better

All of them can be run in the 65,000 PSIA range with good brass.

 

[bigedp51]

interesting discovery, the SAAMi 223 psi is 55,000 normal chambers, and higher for those with longer throats

The chamber pressure for the .223 and 5.56 is exactly the same, "BUT" can be measured three different ways. And yes the throat is longer in a M16/AR15 rifle. And the throat in my Savage .223 is even longer than my AR15 rifles.

.223/5.56 chamber pressures
1. 52,000 cup (SAAMI copper crusher)
2. 55,000 psi (SAAMI transducer method with transducer located at the mid point of the cartridge case)
3. 60,000 psi (European CIP NATO transducer method with the transducer located at the case mouth)

I have the military test requirements for civilian contract 5.56 ammunition for the military and the document lists the two pressures of 52,000 cup or 55,000 psi for American made ammunition. And it is "NOT" the same as NATO EPVAT testing methods using european CIP standards. (62,366 psi max pressure)

And my practice ammo for my AR15 rifles isn't loaded hot to save the stress on my brass and rifles.

 

[bigedp51]

Current Maximum Average Pressure (MAP) for the 223 and 222 Magnum is 55,000 PSI (for BOTH of them) and current MAP for the .221 FurBall is 60,000 PSI. Current MAP for the standard 222 is 50,000.

All of them can be run in the 65,000 PSIA range with good brass.

I remember someone with the screen name of Cat(something or other) posting brass rockwell hardness figures and Remington brass was the softest and Lake City military cases being the hardest of the ones he posted. :

Below are my Remington .223 cases used as blasting ammo in my AR15 carbine and they are loaded to approximately 50,000 psi

So CatShooter, what is "good brass" and why is SAAMI chamber pressure listed as 55,000. :

So define "good brass" I don't want everyone to think that all brass is made Ford Truck Tough, especially when Federal brass is even softer and thinner than Remington.

And you will not see me jacking the chamber pressure up to 65,000 psi on any Remington brass when it ain't built Ford Truck Tough.

Military 5.56 cases are built Ford Truck Tough and Remington and Federal are built like a Dodge or Chevy made on a Friday.

God bless America and thick hard Lake City military brass.

Bazinga ;D