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okie2
February 3, 2010, 10:58 PM
How do they Test a modern bolt action to find it's maxium strenght to the point that it will blow up under pressure.
In other words if our most PSI pressures are now at 65,000 for some calibers how much above that will they stand for safty's sake and liability protection for them.

Scorch
February 4, 2010, 02:15 AM
Metallurgy reference books will tell you the tensile strength, shear strength, and yield strength of different steels. If you know that the largest cartridge to fit inside the action needs X inches of steel at a given pressure to yield or shear the bolt lugs, you increase you calculated metal thickness to give you the needed metal thickness for a 50%-100% overpressure load and make the action accordingly. The calculations are pretty straightforward.

In the old days, they would often take sample actions and fire overloaded ammo in the firearm to test them to failure, nowadays they do non-destructive testing and computer simulation testing of designs.

okie2
February 4, 2010, 04:41 AM
thank you
you hit the nail right square on the head. It always starts a disagreement when you tell some one that does not ever know or think of there being a liability part to this whole deal that 1 more grain of powder over the newer load books that are way under max of even flatening a primer that it will not blow your rifle apart in your face and kill you. But they think they always know what they are talking about.

mapsjanhere
February 4, 2010, 08:16 AM
Please remember that this only applies to US sold rifles. European countries still test fire the gun with a 30% overpressure load.

okie2
February 4, 2010, 08:46 AM
Ok thank you

James K
February 8, 2010, 04:29 PM
American factories prove firearms in the interest of safety. Foreign governments do so both for safety and to control the manufacture of firearms and, sometimes, prevent the importation of arms that would compete with local manufacturers. (The main purpose of the original British proof law was to eliminate Belgian makers from the English market.)

No one uses proof loads of 50 or 100 percent over maximum average. U.S. proof loads run 25-30% above, just as European loads do. The idea is to weed out defective guns, mainly gun barrels, not to blow up half the production. In reality, a gun failing proof is a very rare occurrence today with modern steels and manufacturing methods, but in the days of Damascus barrels and iron frames and cylinders, proof testing was needed, in good part just to reassure the customer that the gun was not dangerous.

Aside from proof testing, which is done for every gun, manufacturers periodically run destructive tests, deliberately trying to find out how much pressure is needed to actually blow up a gun and where improvements can be made. Remington has reportedly tested the Model 700 to 175,000 psi without a failure, but that rifle has a very strong action. Other rifles should still handle much greater than SAAMI average maximum without failure.

The weak point in any rifle is the cartridge case. At very high pressures, brass acts like playdough, and a blown case head will almost always wreck the rifle.

Jim

okie2
February 8, 2010, 06:17 PM
Thank you Jim
The point I'm trying to get to is that all the reload books say do not exceed maxium loads. In which all of the newer books now are not near what max really is because of liability of the powder and bullet companies the max is really maybe 2 to 4 grains higher.
And then you hear from all these people say I'm afraid to load a max load it might kill me. I don't know at what pressure a primer starts to flaten but when I get to that point I call it enough. But at that point I am most always way above the book max load too.
With your information even just 25% over 65,000 pressure is 81,250.
One other question how do you convert cup to PSI pressure or reversed?

mapsjanhere
February 8, 2010, 07:29 PM
CUP and PSI are not directly transferable unfortunately.
As for reloading past book max, you're just counting on your primer being the first thing to give. As Jim said, a gun counts on the brass to contain the pressure to the the barrel, the chamber and the bolt face. If the brass fails first, you're having 80,000 PSI hot gas flowing past the bolt towards your face, taking whatever else in the way isn't designed to withstand pressure with it. With these kind of pressures you're also risking that your bullets might not be able to stand the forces involved, and a stripped jacket stuck in your barrel is going to put a serious cramp on your style when you pull the trigger on the next shot. The lugs securing your bolt are not likely the first thing to give in an overpressure situation (so they might follow the rest for good measure).

okie2
February 8, 2010, 11:13 PM
www.shootingsoftware.com/ftp/psicuparticle2.pdf
open this and read

mapsjanhere
February 9, 2010, 08:26 AM
Very good example, that article you linked, it gives a nice equation to correlate the two units, than adds: About 2/3 of the time, the formula will land you within 3,000 PSI With other words, it's off by more than 3000 psi in 1/3 of the cases. Most reloaders stay away from these kind of guesses, especially around maximum loads.

Wyogoose
February 12, 2010, 03:00 AM
White's labratory will fire your cartridge in a test barrel if the pressure is in question. As far as I know, they will even vary the temperature of the chamber and cartridge for real world presures. The debate will continue on whether the manuals are cheating people out of the last 25 fps, but the line has to be drawn somewhere. I would rather it be on the side of safety. Particuarly for the newb to reloading with a 110 year old action remodeled in his garage to fire a 300 RUM.
Can more velocity be achieved? Maybe. But who can guarantee that the reloading data will be used in brand new action. The minute that it isn't and someone literally loses their head, we all lose. Why would any of us risk another lawsuit to the industry to gain 25 fps???
My thoughts are if you feel comfortable making a load above manual specs, send it out and have it tested before making a blanket statement about how the manual companies are stealing performance. It is the responsible thing to do. How many newbs have been blown up from bad advise? I for one would not want to live with anothers blindness caused by my ego trying to prove a powder company wrong. Especially for even 100 fps

No offense intended, just an observation through my experience,
Rick

Wyogoose
February 12, 2010, 03:38 AM
White's labratory will fire your cartridge in a test barrel if the pressure is in question. As far as I know, they will even vary the temperature of the chamber and cartridge for real world presures. The debate will continue on whether the manuals are cheating people out of the last 25 fps, but the line has to be drawn somewhere. I would rather it be on the side of safety. Particuarly for the newb to reloading with a 110 year old action remodeled in his garage to fire a 300 RUM.
Can more velocity be achieved? Maybe. But who can guarantee that the reloading data will be used in brand new action. The minute that it isn't and someone literally loses their head, we all lose. Why would any of us risk another lawsuit to the industry to gain 25 fps???
My thoughts are if you feel comfortable making a load above manual specs, send it out and have it tested before making a blanket statement about how the manual companies are stealing performance. It is the responsible thing to do. How many newbs have been blown up from bad advise? I for one would not want to live with anothers blindness caused by my ego trying to prove a powder company wrong. Especially for even 100 fps

No offense intended, just an observation through my experience,
Rick