first introduced at, 35000,38500,or somewhere in between?

Compelling question. I don't have the definitive answer but two things occur to me and I would bet that BOTH matter a lot for the "proper" answer.

First is that I don't believe SAAMI existed when the 9mm went mainstream and second is that the pressure testing equipment at that time was not only nowhere as accurate as today, it was also quite likely well out of the realm of many ammo and gun makers.

Old Luger: Euro CIP 34,000CUP
NATO: 36,500 PSI
SAAMI: 35,000 PSI 38,500PSI c/o +P

would be cool to test some early 9mm ammo if even it could be had?

thanks, what is the max psi a 9mm casing can handle, all things being the same, brass case not steel or alm? so +p+ starts at 38,501?

The 9 mm Luger cartridge was introduced in 1902, so I doubt you'll find any pressure data from that era that would be referable to modern standards. I think the ballistics were similar to current standard pressure ammunition.

There is no +P+ standard, so if you want to call it >38,500 psi you can.

I guess what i'am getting at is, if saami set std pressure at 35,000 and +p at 38,500 there must be some head room on virgin brass that the ammo companys know about in order to load +p+ ammo over 38,501 psi, what is the kaboom psi for virgin brass 40,000?

Brass has a lot of spring to it. A "kaboom" happens when the chamber lets go. The brass can handles pressures well over 40,000 PSI assuming the gun can handle it.

Observe that SAAMI and CIP specifications are for MAXIMUM chamber pressure. However, most manufacturers load their ammunition to pressure levels somewhat below maximum. For example, the U. S. Military specification for the M882 9mm round is 34,519 psi (maximum average chamber pressure). Actual production M882 ammunition is held to a MACP of 32,750 psi. There is a little more detail to the pressure specifications, but that illustrates the point.

The brass only expands on it's own until it hits the chamber wall where it then expands along with the chamber.

Another limiter is head separation where the head blows out back of the chamber, but this is usually a gun fitting problem, i.e. not enough support of the case or too much end play where a cartridge can back out and expose too much area .

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great info guys, thank you.

There is also fps vs pressure...........

A load of Unique powder with a 115gr plated 9mm bullet in a 3" barrel
in one of my test reached 1168fps on average.

In a 3.5" C9 pistol this same load reached on average, 1263 fps.

In a 5" barrel this same load reached up to 1350fps but at the same chamber pressure, for a 182fps increase !!

+P+ can be attained but you need to know if the weapon is up to it.

There is actually quite a bit on information on overpressure 9mm ammunition, because some USPSA competitors load "MAJOR POWER 9mm" to shoot in OPEN DIVISION. Our local shooters use HS6 to load to a power factor of 165+, which they typically shoot in STI competition pistols with fully supported barrels. Naturally several shooters have tried them in other pistols, including M&Ps. The M&Ps will fire them without going hand grenade, but you join the "part of the month club" and typically finally break the frame, slide, or both. One of our shooters tried them in a 1911 single stack, and the cartridge blew out the bottom every shot, sending the magazine out, but no other damage to the gun.
The 9mm case alone will not survive any load without being supported sufficiently by the barrel. Cook off a 9mm round lying on the campfire,and the bullet will be lying right there, with the brass blown into tiny dangerous pieces over a wide area.

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The two posts above are spot on target.

In the extreme, I have a few maximum (but still standard pressure) loads that will launch a 115 gr bullet at 1550-1600 fps in my AR-9 pistol and carbine, and my Uzi carbine. Those firearms combine both a much longer barrel and fully supported cases in chambers that are not undercut to accommodate a feed ramp.

It's that unsupported area over the feed ramp where the 9mm Luger case will fail at higher pressures.

On the other hand, with a blow back operated firearm with a comparatively light weight bolt like the AR-9, you'll need a heavier buffer and spring, and perhaps a spacer to reduce the slide over run to prevent breaking the bolt stop over time. The Uzi just shrugs off the hotter loads as its bolt is very heavy.

In most 4" 9mm's, the Federal 9BPLE 115gr +P+ list 1300fps.

Underwood has it's 124gr +P+ going 1300fps +/- out of a Glock19, 4"...............
Check your weapon per it's company to make sure this load is acceptable.
Most 4" pistols are rated for the 124gr +P at 1220fps, as a maximum loading.

"I feel the need for speed" is great for a movie statement but is
hard on a weapon if pushing it to mach two.

That 9mm is amazing - along with 45 acp, why would anyone need another caliber in service type autos...

I recall reading about the Austrian military's plan to replace the current issue P38 back in the early 80's. The bid specs required the new replacement to fire over 10 or 12K rounds of standard nato pressure (36+K) rounds then fire a double pressure round of 72,000PSI without any failure.
Gaston Glock accomplished his with the Glock 17.

72,000 didn't expect that!

It would be interesting to see how long a Glock 19 (4") would hold up with
a case of Underwood 115 and 124gr +P+ factory ammo.

If it would go ten boxes, I would hold its hand up and call it the winner and still Champion..................

Like already said, there is no +P+ standard.

+P+ = over pressure so it's best you don't do it. Since the 9mm case is small and slight changes in powder charge or bullet depth can increase pressures greatly, it's just too dangerous.

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