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Discussion Starter · #1 ·
Looking for some understanding of saami pressure guidelines.
Why is the 44 special 15,500 when the 44 magnum is 36,000?
Another example is the 45 acp rated at 21,000 when the 9mm Luger is at 35,000. I don't understand just what they go by but its got to be something besides age because the 9mm was designed in 1901, 4 years before the.45 acp
Do certain cases have an inherent weakness? I believe a lot of new designs are developed just to get a higher saami pressure rating since there is little difference between say the .45 long colt and the .454 Casull other than it being slightly longer. I could give a thousand other examples but you get the point. Any thoughts?
 

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It's not the cases that are the weak link (except for balloon head cases), it's the guns that they're worried about, specifically the older guns that were made to withstand the pressures of the original rounds but not the pressures that are attainable today.

You have a similar problem, though, if someone decides to make a gun today that will only withstand the pressures from the old days and some do, I'm sure.

Take a look at some reloading manuals and you'll see one section for Thompson Center, another for Ruger and yet a third for all others. You can also see that with some rifle rounds manufactured by places like Buffalo Bore and Garrett.
 

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Discussion Starter · #3 ·
It's not the cases that are the weak link (except for balloon head cases), it's the guns that they're worried about, specifically the older guns that were made to withstand the pressures of the original rounds but not the pressures that are attainable today.

You have a similar problem, though, if someone decides to make a gun today that will only withstand the pressures from the old days and some do, I'm sure.

Take a look at some reloading manuals and you'll see one section for Thompson Center, another for Ruger and yet a third for all others. You can also see that with some rifle rounds manufactured by places like Buffalo Bore and Garrett.
That doesn't explain the 9mm luger. It's older than the .45 acp and there is plenty of old worn out 9mm guns with inferior metals
 

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That doesn't explain the 9mm luger. It's older than the .45 acp and there is plenty of old worn out 9mm guns with inferior metals
Ah, but it does explain the 9MM Luger. It was made to handle the pressures of the round from the start. That's the difference.
 

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What FlashLB said.

There are several factors that go into this.

The gun design, take a Springfield trapdoor 45-70, designed in the 1870's using 70 grains of black powder pushing a 405 grain bullet. This was just before the advent of smokeless powder that has about 3 times the energy of black. And modern guns, such as the Marlin 1895 guide gun in 45-70, have actions designed for higher pressure smokeless powder loads. Reloading manuals will spec the load for being only suitable for modern lever guns, as will be the case for boxes of ammo too. If it's not spec'd, or states something like, "suitable for all", then it's lower velocity.

It's interesting some may consider cartridges such as .38 Special and .44 Special as being modern, when they were originally designed for black powder, and thus you find a 17,000 psi SAMMI spec for the .38 and lower for the .44. They use smokeless, of course, but either less powder or a slower burning powder to keep pressures down. So when going from .38 to the relatively modern .357 cartridge in a wheel gun, not only in the .357 a bit longer (so you go, yeah, it's got more power), SAMMI spec pressure is double!
 

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Discussion Starter · #7 ·
Ah, but it does explain the 9MM Luger. It was made to handle the pressures of the round from the start. That's the difference.
What is designed for it? The brass? The .45 is inherently weaker that 9mm Luger?
If that's true and I wouldn't argue it isn't I still don't understand the huge pressure difference, a few thousands psi ok but almost double!
 

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What is designed for it? The brass? The .45 is inherently weaker that 9mm Luger?
If that's true and I wouldn't argue it isn't I still don't understand the huge pressure difference, a few thousands psi ok but almost double!
No, it's the guns. All brass except for the old balloon head stuff can take about the same amount of pressure.

Oh, and you can get close to .357 magnum velocity and pressure in the .38 special case, but the manufacturers wisely made the .357 magnum 1/8" longer so it wouldn't chamber in the .38 special guns. They weren't made to take the pressure of the .357 magnum.
 

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Discussion Starter · #9 ·
What is designed for it? The brass? The .45 is inherently weaker that 9mm Luger?
If that's true and I wouldn't argue it isn't I still don't understand the huge pressure difference, a few thousands psi ok but almost double!
What I'm trying to say is if you have a sig 226 in 9mm and one in .45 and they are identical
Why would it matter what case was in it 30,000 psi is 30,000 psi. The only difference would be the inherent strength of the case. Hard to believe a.45 case is that much weaker than a 9
 

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Rickey Mitchell;

First off, welcome to the forum.
In my honest opinion after reading more of your posts/questions, it is not understanding SAAMI spec's and regulations but you need to wrap your head around "internal ballistics".

After understanding internal ballistics, then SAAMI is obvious.

A lot of good text out there on internal ballistics.
Then read about external ballistics.
There is a whole new world out there to discover when we start to read and learn and then take the plunge to reload our own ammunition.

It is a great journey, sit back and enjoy.

Clarence
 

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What I'm trying to say is if you have a sig 226 in 9mm and one in .45 and they are identical
Why would it matter what case was in it 30,000 psi is 30,000 psi. The only difference would be the inherent strength of the case. Hard to believe a.45 case is that much weaker than a 9
And I keep telling you it isn't, and you don't believe that for some obscure reason.

I give up. Go read some books on the subject and get back to us.
 

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Discussion Starter · #12 ·
Rickey Mitchell;

First off, welcome to the forum.
In my honest opinion after reading more of your posts/questions, it is not understanding SAAMI spec's and regulations but you need to wrap your head around "internal ballistics".

After understanding internal ballistics, then SAAMI is obvious.

A lot of good text out there on internal ballistics.
Then read about external ballistics.
There is a whole new world out there to discover when we start to read and learn and then take the plunge to reload our own ammunition.

It is a great journey, sit back and enjoy.

Clarence
I'll do that and thanks for the information. I a just trying to understand and figure out the difference in pressure designations for specific ammo.
Appreciate your and LB flash's response
 

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Rickey;

Most are here to help as I.
I had the same type of questions in my head 30+ years ago when I got really involved in firearms.
Did a lot of research, reading and learning from text sources(not the internet:D)

Clarence
 

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What I'm trying to say is if you have a sig 226 in 9mm and one in .45 and they are identical
Why would it matter what case was in it 30,000 psi is 30,000 psi. The only difference would be the inherent strength of the case. Hard to believe a.45 case is that much weaker than a 9
It's not about the case! The case has two functions, to hold the other components in place ( powder, bullet and primer) and to provide a seal with the barrel's chamber walls to prevent gas blow back upon ignition. The cartridge case walls near instantaneously expand outwards applying thousands of pounds per square inch against the chamber walls for a gas tight seal - there is little strength in the brass, almost all the strength to withstand that pressure is provided by the chamber's steel walls and the mechanical lock up mechanism which holds the breach face in position to prevent it from being pushed back allowing the cartridge case to "blow out".

This chamber pressure can be so great, it can cause the brass to flow, as often happens in rifle cartridges, making the case longer. It also increase the diameter of the case as it stretches to conform with the chamber surface. The breech face (headspace) limits the case's rear movement - the only area of the case that needs to be truly strong is the transition area that is unsupported between the base and the case wall. After ignition and bullet departure, pressure drops and the brass elasticity allows to "shrink back" a little towards it's original size, and in doing so, this allows extraction from the chamber.

Consider the case on a lowly .22 short rimfire would be blown to smithereens if it were not supported by the chamber and breech face. It's about what the original gun/s that were built for the cartridge were designed and proofed for.

In the case of the .44 Special you mentioned, that was originally a low pressure (by today's standards) early smokeless powder cartridge based on the 44 Russian black powder cartridge, lengthed a little. Even then, performance was not better than the black powder cartridge it was based on.

Often, as in the case of the .45 ACP, it's probably more about metallurgy, as the underlying design is the same. SAMMI for the .45 is 21,000 psi, yet the similar 1911 made for the 10mm, is at 37,500. Gun appearance similar, pressure near double. I would not be brave enough to load up a 45 cartridge to 10mm specs and shoot it in a WWI era Colt.

Smokeless powder, metallurgy, and in many cases gun design has improved to safely withstand still higher pressures.

44 Special, 15,500 psi

454 Casull, 65,000 psi . . . More than 4 times the pressure! I only shot my son's Ruger SA 454 once - good enough. I was hanging onto that gun like I was one grip away from certain death rock climbing - - and it still managed to come back and smack my middle finger hard enough to where i just handed that sucker back to him.
 

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Discussion Starter · #15 ·
It's not about the case! The case has two functions, to hold the other components in place ( powder, bullet and primer) and to provide a seal with the barrel's chamber walls to prevent gas blow back upon ignition. The cartridge case walls near instantaneously expand outwards applying thousands of pounds per square inch against the chamber walls for a gas tight seal - there is little strength in the brass, almost all the strength to withstand that pressure is provided by the chamber's steel walls and the mechanical lock up mechanism which holds the breach face in position to prevent it from being pushed back allowing the cartridge case to "blow out".

This chamber pressure can be so great, it can cause the brass to flow, as often happens in rifle cartridges, making the case longer. It also increase the diameter of the case as it stretches to conform with the chamber surface. The breech face (headspace) limits the case's rear movement - the only area of the case that needs to be truly strong is the transition area that is unsupported between the base and the case wall. After ignition and bullet departure, pressure drops and the brass elasticity allows to "shrink back" a little towards it's original size, and in doing so, this allows extraction from the chamber.

Consider the case on a lowly .22 short rimfire would be blown to smithereens if it were not supported by the chamber and breech face. It's about what the original gun/s that were built for the cartridge were designed and proofed for.

In the case of the .44 Special you mentioned, that was originally a low pressure (by today's standards) early smokeless powder cartridge based on the 44 Russian black powder cartridge, lengthed a little. Even then, performance was not better than the black powder cartridge it was based on.

Often, as in the case of the .45 ACP, it's probably more about metallurgy, as the underlying design is the same. SAMMI for the .45 is 21,000 psi, yet the similar 1911 made for the 10mm, is at 37,500. Gun appearance similar, pressure near double. I would not be brave enough to load up a 45 cartridge to 10mm specs and shoot it in a WWI era Colt.

Smokeless powder, metallurgy, and in many cases gun design has improved to safely withstand still higher pressures.

44 Special, 15,500 psi

454 Casull, 65,000 psi . . . More than 4 times the pressure! I only shot my son's Ruger SA 454 once - good enough. I was hanging onto that gun like I was one grip away from certain death rock climbing - - and it still managed to come back and smack my middle finger hard enough to where i just handed that sucker back to him.
Hey thanks Bumper,lots of great information there. It all brings it back to my original question. Why is the 9mm Luger pressure so much higher than the .45 auto.
As stated the 9 Luger is older than the .45 and I'm sure the guns for both had inferior metals. There are many hundreds if not thousands of gun manufacturers with various skills in metallurgy.
To me there is no logical explanation for the pressure difference . I own p220's in both .45 and 10 mm and sig will not even recommend plus p's in the alloy framed .45 which is 23,000 psi while the 10mm is at 37,500
This site has a lot of very knowledgeable people, more so than any other site I've been on and I just wanted some thoughts on the subject.
One of the things that got me going on the subject was 40 S&W owners saying that it is almost an equal to a .45. We'll look at the pressure difference, 21,000 vs 35,000. Lets load the .40 at 21,000 and then compare, I do own 4 .40's and like the round.
 

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Rickey. First off Welcome.

Second, we need to look at the Ammunition Requirements for the .45 ACP weapon. In the time of the adoption.

The .45 ACP was designed to "Emulate the ballistic behavior of the production .45 Long Colt revolver" that is what the Army wanted. Big Ugly bullet moving at 850 FPS. Like the Colt did.
TO do so, the ACP had to have higher working pressures then the .45 LC did because of the smaller case. (14000 for the LC, 19000 for the ACP)

So, it was backwards engineered to replicate the performance of the cartridge already used.

The 9X19 was developed from a different mindset. The goal there was to take an existing Police cartridge (the 9MM Kurtz) and provide additional power "For War" (which is what Parabellum means) in the 1902 trials from Luger. And to do this we had to take the original 7.65 Luger, open the case up to 9MM, and add some steam to it.

And there we had the beginning of the Famous Pistol Cartridge Wars. So we have a 230 grain bullet moving at 850 FPS or a 9MM 115 grain bullet traveling at 1300 FPS. the Parabellum having 1/2 the weight moving 500 FPS faster.

Which way do we go? High Speed, Small bullet? Or Hit em with a Bowling ball?

That is the basis of the argument.
 
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This is some great information here. Definitely one of the better sites I've been on. I have to agree that the .45 ACP and 9mm parabellum/Luger each represent two schools of thought that are still debating each other today. It all boils down to the velocity or mass debate. Which is more important? A smaller projectile moving faster or a larger object hiring with more mass. The.45 ACP is designed to hit with the authority of a small boulder and create a wider wound channel. However, the 9mm penetrates a bit deeper than the .45ACP so even though the wound channel is narrower the increased penetration is much more likely to kill than its 9mm kurz predecessor.
 

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The thing I think that is being presented here is that it's all a moot point in terms of lethality to compare .45ACP to 9mm parabellum. Both calibers get the job done (within a reasonable margin of error) for different reasons. Wider wound channel= more difficult to heal and likely to shave a vital organ or a narrow deeper wound channel= easier to sew up but more susceptible to internal bleeding
 
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