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does a 9mm stress and abuse a frame like a 357 magnum?

Discussion in 'Handguns: General Discussion' started by jason41987, Nov 29, 2012.

  1. jason41987

    jason41987 member

    just a hypothetical on chamber pressures... but 9mm loads are often around 35,000 PSI, heck, getting hard to find a 9mm load under the SAAMI max for standard pressure... 357 magnum is around 35,000 PSI...

    so given these cartridges are close in outter diameter, if both rounds are placed into similar chambers, with similar thicknesses, shouldnt the 9mm cause about as much damage to the chamber as a 357 magnum would as both are causing roughly the same amount of PSI?

    now lets take a larger caliber... lets say 44 magnum... lets say this is placed into a chamber, whos wall thicknesses are the same as the wall thicknesses for the 357 magnum, at roughly the same PSI, would it also be true that the 44 mag wouldnt do any more damage to the chamber than the 357 magnum?

    i often hear people say 9mm is nothing more than a longer 380... my response tends to be "no, its more like a shortened 357 automag" would you agree with this statement?

    this thread isnt for some kind of project, or idea.. just to gain further knowledge on how chamber pressures and chamber thicknesses relate to eachother for the safe firing of the cartridges
  2. Remllez

    Remllez Well-Known Member

    I agree with your general statement that 9mm is closer to .357 however I'm not sure what kind of cylinder damage you are speaking of. Properly designed guns for caliber may show signs of normal and acceptable wear, but to call it damage is a bit extreme to my way of thinking.

    Just my .02
  3. rcmodel

    rcmodel Member in memoriam

    Not sure what kind of "chamber damage" you are referring too, as there is none with any caliber in a properly designed gun.

    At some point well over the 35,000 PSI load, chamber damage would result in a bulged chamber.

    At even higher pressure, well over 70,000 PSI, such damage will progress to the chamber blowing up, shearing the top three chambers off the cylinder, and blowing the top strap off the revolver.

    That is more likely to happen with the magnum revolver calibers, because the cases are bigger, hold more powder, and especially make a double charge more likely.

    A double charge in a 9mm case simply won't fit, and would surely be noticed by a reloader.

    But in normal pressure loads, be they 9mm, .357, or .44 Magnum, there simply is no chamber damage with SAAMI spec load pressure.

  4. Wil Terry

    Wil Terry Well-Known Member

    LET ME SEE HERE.....My S&W M19 4" has 49,000 rounds though it and the frame is in fine shape. The CYLINDER is in fine shape. The forcing cone as issued is all but gone, but the gun still shoots up a storm and is still faster than any 6" 357MAG I ever chronographed [ about 100 guns ]
    ALL of my formerly owned 9MM PARABELLUM sixguns were puny in comparison. The only one I bothered to keep is a 3" M940.
  5. ATLDave

    ATLDave Well-Known Member

    Disclaimer: I claim no expertise in this area.

    Agree with prior responses. Also, you may be overlooking a factor in a pressure situation - area. 10 psi won't inflate a car tire, but 10 psi (or half that) applied uniformly across a wall will knock down a building (see fuel air explosives). So a smaller cartridge may be operating at the same pressure as a larger one, but it is NOT exerting the same amount of force on the chamber walls.

    One other note. Long-term, or even catastrophic short-term, damage from over-pressure cartridges isn't primarily about the chamber. Things like frame-strech (common on some .357's) or "kabooms" aren't chamber-oriented. The brass of the cartridge is much soften than the steel chamber, and will fail before the chamber does. When that happens, you'll blow high-pressure gas elsewhere in the gun. Of course, if you've got a barrel obstruction, something has to give, and that's usually the barrel, though it could be the chamber if the obstruction was very close, and the action locking mechanism was quite strong. Can chambers be damaged? Yes. But that's not usually going to be the first thing to go. If you've managed to blow up the chamber (usually the very strongest part of the gun), you've really done it.
  6. eldon519

    eldon519 Well-Known Member

    Aside that neither cartridge should cause damage in a chamber in general, you would need thicker walls for the .44 magnum given the same PSI to cause the same stress in the metal. The smaller the caliber, the less wall thickness you need for the same PSI.
  7. hardluk1

    hardluk1 member

    In the case of a 9mm it would depend on the handgun, the cycle speed the metal the slides made from and how it is treated. 9mm in a full sized pistol compaced to a pf-9 would be lik e 357 in a sw model 19 compaired to a 27 or 28. Over time it will cause damage to the lighter built firearms.
  8. NG VI

    NG VI Well-Known Member

    Chamber pressure is only part of the equation, recoil forces and gas volume are probably more important.

    Chamber pressure measures the peak pressure, but it is entirely possible to have a cartridge that generates far more forces on the firearm while generating lower chamber pressure. A small case with low gas volume could generate more pressure while actually delivering much less power and recoil forces than a somewhat larger case that has the ability to generate more gas volume.
  9. 9mmepiphany

    9mmepiphany Moderator

    You might have just used the wrong nomenclature, but I somewhat doubt you meant that the 9mm was just a shortened .357 Automag ...which is a necked down .44 Automag.


    The .380ACP is commonly known as a 9x17mm, while the 9mm is a 9x19mm, so it isn't a completely inaccurate statement. It is much like the relationship between the .38 Spl and the .357 Magnum...with the longer case allowing a heavier load of powder. The bigger difference is that the 9x17mm is usually the upper practical limit for a blowback action pistol; The 9mm is a blown out .30 Luger case
  10. BCRider

    BCRider Well-Known Member

    Jason, as pointed out your use of the term "damage" was a bad one. But I think I know what you meant as do most of the others.

    In any event what happens is that the steel of the chamber in the barrel or chamber in the cylinder does stretch a little under the pressure. The key is that the stretch is within the elastic limits of the material so the chambers spring back instead of suffering from any damage or permanent deformation.

    And as mentioned due to how the pressure works in a pipe or other tubular style vessel the bigger the bore the thicker the metal needs to be if it's to resist the same pressure. There's a bunch of physics and math that goes with this but the bottom line is that for a given pressure the wall has to increase in thickness for an increase in the bore diameter.
  11. jason41987

    jason41987 member

    yeah, damage was probably a bad term, i was referring to the stresses felt by the metal... i wonder how much bullet size factors into this... a bigger bullet will take more energy to get moving, and hold higher pressures for a longer period of time as opposed to a smaller, lighter bullet

    as for automag, i was referring to essentially taking a 5.56x45mm cartridge, chopping it down to 357 magnum length and loading it accordingly as a rimless 357.... take that, chop it down to x19mm at the same pressures and youd roughly have a 9mm cartrdge....

    so to put this into something more practical, an action of any type of firearm that fires a cartridge that produces a certain amount of pressure, could potentially be chambered into any cartridge that can fit within the constraints of the action, so long as that pressure it was designed for is not exceeded

    just trying to understand the phyiscs around chamber pressures a bit more
  12. grizz13

    grizz13 Member

    I'm not sure about frame stretching or anything like that but just relating cylinder thickness the stress in a thick wall cylinder is represented as

    pressure x average of internal radius and external radius / wall thickness

    So from this the pressure and wall thickness would stay the same and the average radius would change.

    9mm avg. radius > .357 average radius so the 9mm would result in a higher stress on the chamber and more damage. But with a difference of .001" at the mouth and .011" at the base the difference would be very small.

    So a .44 caliber round would result in much higher stresses on the chamber at the same pressure and wall thickness. Hope that answers the question you thought you asked ;)
  13. barnbwt

    barnbwt Well-Known Member

    Yup, you need to be looking at pressure with regards to chamber design, but bolt thrust for bolt/lock design, and recoil for bulk frame/stock design (I'm guessing this is a design question, based on queries you've posted in the past ;))

    I looked into this science recently regarding M95 rebarrel to 45/70;
    Chamber Pressure Regarding Cartridge Selection
    and a (suprisingly) helpful Wikipedia article on the subject:
    Bolt Thrust

    I'd neglect any effect brass friction may (or may not) have on the bolt thrust numbers, as NATO does for weapon design calculations/proofing.

    ProofPressure*CaseHeadArea = Bolt Thrust (conservative estimate; peak load, no case friction, outside casehead area)
    Pressure*ChamberRadius/Thickness = Thin Wall Stress (I don't think this is conservative for thick walls; check before using it)
    Thick Wall Stresses are derived from the Lame Equations and are a bit more complicated (stress varies radially, unlike thin-walls). Use an online calculator (even then, a revolver chamber isn't a simple tube, so values may be off some)
    Recoil can be found with online calculators and is based on powder/charge, pressure, bullet weight, velocity, and more--I'd use the Quickload program, which takes these many factors into account for you, but costs money

    Last edited: Nov 29, 2012
  14. 1911Tuner

    1911Tuner Moderator Emeritus


    Pressure isn't the only concern, and in many guns...it's not even the main concern.

    Comparing a known high-pressure cartridge like the .22-250 and a known low pressure number like the .45-70 loaded with a 405-grain bullet and 70 grains of black powder...which one will deliver higher bolt/breechface thrust and thus the higher level of stress?

    Also, when comparing autopistols to revolvers, the stress isn't on the frame of the auto. It's on the slide and...in the locked breech design...the mechanism that keeps the slide and barrel connected. We'll call this mechanism the locking lug or lugs...which differ very little from the big recoil lug on a bolt-action rifle receiver.

    With the autopistol, the "gun" is comprised of the barrel and slide assembly. The frame is essentially little more than the gun mount, and the only connection between the gun and the mount is through springs. The slide serves in the role of breech bolt. A sliding or reciprocating breech bolt not all that much different than that in a Model 94 Winchester carbine.(Which incidentally is locked by a falling block similar to that in a Sharps rifle.)

    In the revolver, the breech bolt/block is an integral part of the frame and all recoil forces are transferred directly to the frame, as well as the resultant tensile stresses imposed between the barrel and breech block. In layman's terms, this is called 'stretch" and it does happen. In an autopistol, the stretch occurs between the locking lugs and the breechblock...which would be around the ejection port.
  15. 481

    481 Well-Known Member

    Perhaps the term you are looking for is "fatigue"?
  16. Ken451

    Ken451 Well-Known Member

    It all depends on how well the individual gun is designed and built. Chamber pressure is meaningless without reference to what the gun was built for. Some guns are designed for light duty use, others are built for much higher volume use.

    I have serious doubts about that.

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