Question concerning .30-06 SAAMI pressure limits


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ojibweindian
January 20, 2004, 01:48 PM
Why is the .30-06 limited to 50,000 CUP while the .308 Winchester has 60,000 PSI as its limit? Does this have to do with the great number of surplus weapons from < the 1950's? that are chambered in .30-06?

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R-WEST
January 21, 2004, 11:30 AM
I think that's pretty much it. A lot of 100 year old '06's out there floating around. Like someone said, onions and wine are the only things that get stronger with age. :)

R-WEST

Black Snowman
January 21, 2004, 01:26 PM
When the -06 round was introduced back in 1906 it was a LOT more expensive to make a gun handle that jump from 50,000 - 60,000 PSI. With the more modern machining and metalurgy after WWII the higher pressure cartridge allowed the military to have a balisticly similar round that was smaller and lighter and could be used in smaller weapons. It's just the march of progress :)

Jim Watson
January 21, 2004, 02:28 PM
They are not all that different. It is the measuring systems that are different.
50,000 CUP is very close to 60,000 psi.

Lyman 47th has both in CUP, .30-06 up to 50,000, .308 up to 52,000 for maximum loads.
For some strange reason Accurate Arms tested .30-06 in psi with maximum loads of 60,000 psi and .308 in CUP, up to 50,000 CUP maximum.

There is opportunity for confusion. Copper crusher readings USED TO BE recorded as psi because they were calibrated with hydraulic pressure or a dead weight load which are easily read in psi. Now the term CUP (copper units of pressure) is used for the crusher gauge and psi is limited to electronic transducer readout.

The number given in CUP is lower than the electronic psi reading for the same round because it takes time and energy to compress the copper insert and it just cannot respond fast enough to indicate the peak pressure that the transducer can catch.

ojibweindian
January 21, 2004, 06:13 PM
Okay, I get it.

Now, I have another question. Generally speaking, would my Winchester M70 in .30-06 handle pressures that were a little above SAAMI specs? Not that I would intentionally push things, but I have no reliable means of measuring pressure.

dakotasin
January 21, 2004, 09:25 PM
i sure wouldn't push a winchester very hard.

why worry about the 308, anyway? the 30-06 runs a little above - a lot above the 308, anyway... if you need more performance out of a 30 cal, go magnum.

ojibweindian
January 22, 2004, 09:10 AM
dakotasin

I'm not looking to turn a .30-06 into a magnum; I just want to make sure that if I make a stupid error, I won't most likely pay for it by having to pull the bolt out of my forehead :D

HankB
January 22, 2004, 09:59 AM
SAAMI doesn't seem to make pressure specs available on line. From generally published data, the .30/06 cartridge appears to be loaded to lower maximum pressures than other cartridges based on the same case head diameter, such as the .308, .270, and .280.

There's no reason for this other than the presumed antiquity of some old rifles which may not be up to the strength of modern bolt actions.

As for the Model 70 . . . well, the same action is used for belted magnums, whose larger case diameters leave less steel around the chamber, and which have larger case heads which will increase bolt thrust. A "mere" .30/06 ought to have a bigger safety margin than any of these cartridges.

Unless damaged or defective, I don't see the action letting go unless you're way, WAY above pressure limits. And if you're "working up" to the maximum in small increments (as described in all the major reloading manuals) and paying attention to seating depth of your bullets (don't jam them into the rifling) then you'll see signs of excess pressure on the case long before you're in danger of blowing up the rifle. (The brass will start to "flow" before the gun blows up.)

For maximum velocity, as a very rough rule of thumb, the double base powder which requires the heaviest powder charge to reach maximum safe chamber pressure will deliver maximum velocity.

For a .30/06 using 180 grain bullets, I've had good results with ReLoder 22 powder. Nosler recommends 61.0 grains as max in their manual, and Speer goes up to 62.0. Start around 55 grains, and work up carefully in 1 grain increments, looking for signs of excess pressure at each stage. I use Winchester brass and primer, with a Nosler Partition bullet.

I've never felt any real need to go above this published data, but if you do, you're on your own. ;)

Clark
January 22, 2004, 02:46 PM
Paul Stephens posts that he copyrighted a list of SAAMI pressures 1999, 2000, 2001, 2002, 2003 that claim that 50 kcup for the 30-06 is 60 kpsi.
PaulS thread (http://www.thehighroad.org/showthread.php?s=&threadid=35287)


Denton, self professed statistics nerd, has a formula
ANSI PSI = -17902 + 1.51 x ANSI CUP
Plugging the 50kcup into Denton's fomula:
PSI = -17902 + 1.51 x 50k
50k cup = 57,598 psi
link to thread with formula (http://www.accuratereloading.com/ubbthreads/showflat.php?Cat=&Board=UBB6&Number=529097)

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