Statistical Evidence That Higher Pressure Rounds Wear Out Guns Quicker

[Trunk Monkey]

I have read in a couple of places that firearms chambered in .357 Sig or .40 S&W have a higher failure rate and wear out quicker than guns chambered in 9mm or .45 ACP.

Is there statistical evidence to support this or is the evidence all anecdotal?

 

[justin22885]

its not the pressure, its the bolt thrust.. bolt thrust is calculated by the surface area of the inside base of the cartridge in square inches by the chamber pressure of pounds per square inch. 40S&W, and 9mm have the same pressure but because the 40S&W case is larger in diameter it has as much bolt thrust as a 10mm, 9mm can be pushed up to much higher pressures while still yielding less bolt thrust which is one of the reasons you'll never see 40S&W exceed 9mm by any large margin without damage

so its not the pressure its the bolt thrust

 

[eldon519]

I think what truly wears out the gun is recoil and slide velocity causing the guns to batter themselves to death. Both are related to bolt thrust.

What he said about bolt thrust is exactly right. That's also why it doesn't really make any sense for someone to tell you that in terms of firearm life/wear you'd be better off getting the .40 or 357 SIG version of a gun instead of running 9mm +P+, especially for variants like a Glock where they use the same recoil spring, locking lugs, etc.

 

[barnbwt]

Here you go;

 

[atblis]

I dont think it that simple with regards to pressure and bolt thrust. 357 Sig is a higher pressure round than 10 mm with the same sized case head. Full tilt 10 mm loads would eat a 9/40/357Sig sized gun for lunch. In reality, 40 isn't that far off from 10 mm. 35 v 37.5 kpsi.

40 will handily outrun 9x19 while staying inside SAAMI pressures. How long will a 40 hold up pushing 135s at 1500 fps. Don't know.

 

[M-Cameron]

i think a more important question is......does anyone actually know of someone who has managed to "wear out" a .357sig or .40sw.....?

i mean, assuming your gun lasts for 100K rounds.....thats around $40,000 in ammo.

if you can afford to shoot $40K in ammo......i dont think spending $600 to replace a gun is a huge deal for you.

 

[Trunk Monkey]

Can someone explain bolt thrust please?

barnbwt can you explain that chart?


ETA I don't reload or use hot loads I practice with standard WWB

 

[Destructo6]

i think a more important question is......does anyone actually know of someone who has managed to "wear out" a .357sig or .40sw.....?

Yes, lots of them. Not in 100k rounds, more like 7-10k rounds.

Fairly typical failure being cracking/breaking off of the tab at the front of the milled steel slide, where the recoil spring goes through.

 

[Desertrat357]

How long will a 40 hold up pushing 135s at 1500 fps. Don't know.

That's an excellent question. But I would say a 135 gr at 1500 fps isn't the typical load ran in say a Glock 23. At least not by me. I don't disagree that there is more bolt thrust created by a 40 S&W than a 9mm at the same PSI. My only simpleton thought is wouldn't the larger area of the 40 spread out the effect of that bolt thrust over a larger area of the slide?

I am sure I am wrong on that thought. But that is why I included my simpleton disclaimer My question would be this: It is pretty much general consensus that the 40 S&W will wear out a gun more quickly then a 9mm in the same platform. But how much quicker? Not necessarily a super light super fast load. But how fast would one wear out say on a diet of 180 gr bullets at 950 fps? And for the average shooter is the accelerated wear even going to be noticeable?

 

[M-Cameron]

Yes, lots of them. Not in 100k rounds, more like 7-10k rounds.

Fairly typical failure being cracking/breaking off of the tab at the front of the milled steel slide, where the recoil spring goes through.

which guns? shooting reloads or +p?

i have a hard time believing that any modern handgun is going to "break" in 7,000 rounds.......especially at the location you described....

 

[tarosean]

Go to a competition like USPSA and you will see Open guns and Limited guns break routinely. While the Open guys are generally shooting 9mm Major/38Super/ 38 Supercomp/etc. Limited guns are shooting 40 Major (well the smart ones are)
Being able to take a beating day in and day out is the reason these divisions are ruled by 2011's...

 

[stoky]

 

[Jim Watson]

I take a lesson from Glock.
There are a lot of Glock 17s with amazingly high round counts.
Yet Glock went to a complicated multi-piece recoil spring system in their Gen 4.
I think that was to increase service life of the .40s. Their 9mms have gotten along fine.
Probably just wanted commonality of parts across as many models as possible.

 

[Trunk Monkey]

Does anyone want to take a shot at explaining "Bolt Thrust"?

 

[justin22885]

Can someone explain bolt thrust please?

barnbwt can you explain that chart?


ETA I don't reload or use hot loads I practice with standard WWB

i already explained bolt thrust, its the forces a cartridge case applies to the bolt face when the weapon is fired, the chamber pressures impinging on the inside bottom of the case creates a force of its own equal to the chamber pressure multiplied by the surface area of the inside bottom of the cartridge case

an example, is a 5.56/.223 cartridge case has an internal diameter at the base of about .300" we calculate this surface area with the formula for calculating the area of a circle (pi x R squared), the radius being half the diameter would be .15", so the area comes out to 0.0706858 in2, we multiply that by the chamber pressure of 62,366 PSI.. so 0.0706858 x 62366 = 4408.3906028 pounds of thrust pushing backwards against the bolt in a 5.56 rifle

most people do not need to know the information above, but this is 40S&W even though loaded to the same pressures as 9mm, delivers more thrust and therefor more impact against the frame and/or the slide stop lever and the hole its pinned through, this is also why i refuse to buy anymore handguns with aluminum frames.. i like products that'll live long enough to pass on for generations

 

[TimSr]

Does anyone want to take a shot at explaining "Bolt Thrust"?

I'll take a shot and explain it in layman's terms as how hard the moving parts get slapped around for a given round.

I think simple physics would suggest that a round with higher pressure would wear faster than a lower pressure round from the exact same gun. That doesn't mean either would occur in your lifetime.

I also think that simple physics would suggest that outside of a hotter or softer load for the same caliber, that two different rounds are not fired from the exact same gun without some change in physical characteristics of the gun to accommodate the cartridge which is probably taken into consideration when designing the weapon.

 

[unspellable]

slide velocity

“Bolt thrust”, more properly called “back thrust” is the force the base of the case exerts on the breech face. As stated above it is the pressure multiplied by the internal base area of the case.

However, it’s not the main factor in wear. The impulse is the bullet weight multiplied by the velocity plus the powder weight multiplied by the gas escape velocity. (For pistols the rule is 1.5 times the bullet velocity.) Divide this by the upper weight (slide plus barrel) and you have the slide velocity. Note that this calculation ignores the recoil spring. The recoil spring strength is calculated to bring the slide velocity down to a reasonable level by the time it hits the rear stop.

A stiffer recoil spring will slow the slide more at the expense of hitting the forward stop faster.

It’s the slide velocity and hitting the stops that causes the wear. (Ignoring wear on the bore and lock work.)

 

[MachIVshooter]

Yes, lots of them. Not in 100k rounds, more like 7-10k rounds.

Fairly typical failure being cracking/breaking off of the tab at the front of the milled steel slide, where the recoil spring goes through.

Models? Pictures or other proof? Documentation that they weren't fed a diet of Clark-level loads?

I'm with M-Cameron; never heard of a quality pistol wearing out in <10K rounds, save for true micro guns. Some may suffer a part breakage, but that is wholly different from "wearing out". It's also extremely uncommon for it to be the guide rod tang on the slide which lets go.

so its not the pressure its the bolt thrust

Nope. That would be the case only if you were seeing shearing of the lug(s) on locked breech pistols, the majority of which are the leading edge of the chamber in modern designs. Pretty uncommon failure point.

It is slide velocity that batters semi-automatic handguns. Slide cracking at the ejection port could be partially attributed to thrust, but is more likely inertia, the heavier portion of the slide rear of the port trying to tear itself away from the front half that is stopped when it bottoms out the recoil spring.

This is the reason that pocket guns do not have the lifespan of larger counterparts; the lighter weight slides are moving at higher velocity, in accordance with Newton's 3rd law. Ergo, they are more abusive to themselves and the frames.

Now, where revolvers, derringers, single shots or other pistols with a fixed breech are concerned, yes, thrust is the primary factor, as it is acting to separate the chamber(s) or barrel(s) from the breechface with each shot. Is why smaller framed revolvers like the S&W K frames will "shoot themselves loose" if fed a steady diet of really heavy loads, which stretch the frame and batter the forcing cone, causing end shake and loose lock up.

 

[justin22885]

It is slide velocity that batters semi-automatic handguns. Slide cracking at the ejection port could be partially attributed to thrust, but is more likely inertia, the heavier portion of the slide rear of the port trying to tear itself away from the front half that is stopped when it bottoms out the recoil spring.

this is true about the slide velocity, however the back pressure plays a big role in how fast that slide moves rearward against the weight of the slide before it unlocks

i wonder what would be LESS damaging to a frame, a heavier slide which will absorb more of that energy and travel slower, but carry with it more momentum as it slaps the frame, or a lighter slide which will carry less momentum, but travel backwards at a higher velocity?

 

[justin22885]

aluminum frames are generally weaker than steel, this is no secret, its just physics that in equal volumes, steel is much stronger than aluminum and since no more material is added between an aluminum frame vs a steel one, its going to be weaker, theres no way around this, it will wear out in a shorter period of time than steel, this is why the military is having problems with beretta frames wearing out so quick while in military services they have rebuilt 1911s on frames that have been in circulation since WWII with hundreds of thousands of rounds through them

alternatively, polymer framed pistols which contain steel reinforcements, like a glock has steel where it actually matters and these frames can last pretty much as long as steel, yet remain lighter because its made up of polymer in areas that dont need the added reinforcement

as far as im concerned, i'll deal with a little weight as a tradeoff to having a solid, durable, high quality pistol that'll live longer than i will for most purposes, and when it comes to conceal carry i prefer straight blowbacks anyway which are lighter simply because theres less to them, but generally still made of steel

 

[Trunk Monkey]

Thanks for the answers so far now another question

All other things being equal would the wear factor alone cause you to choose a lower pressure pistol over a higher pressure pistol (for the sake of using essentially identical examples, M&P9 V. M&P40)

 

[M-Cameron]

All other things being equal would the wear factor alone cause you to choose a lower pressure pistol over a higher pressure pistol (for the sake of using essentially identical examples, M&P9 V. M&P40)

not at all......i choose the round for the task at hand.......and i choose the gun based on the ergos and features i want.

honestly, unless i know that for some reason, i NEED a gun that will last 300K rounds......"wear" is not even a consideration.

 

[unspellable]

Stretched revolver frames are an urban myth. Metal doesn't stretch until stressed past the yield point, way beyond even any sem-sane load. They do shoot loose. Take the cylinder off the crane of a Smith and look at the yoke tail and the bottom of the cylinder well and you will see where the battering occurs. That's the Achilles' heel on a Smith. Conversely, a Blackhawk cylinder has a bigger area at the gas ring bearing against the frame and so stands up to heavy loads better,

 

[spazzymcgee]

High quality handguns are extremely unlikely to "break or wear out" in less than 10,000 rounds. Ask the serious competition shooters how many rounds they've shot through their guns, and the answers are often over 50,000 rounds.

As far as choosing a lower pressure cartridge due to wear factor alone? I don't think it's a reasonable thing to worry about. You're not going to wear out any gun, regardless of the cartridge it fires. There are a million other factors to be concerned about with cartridge choice.

 

[justin22885]

i dont choose 9mm over 40 because of frame wear, i choose 9mm over 40 because i quite frankly dont see any reason to have a 40.. its overpriced, chambered in frames generally too small for it and offers little improvement ballistically