‘Tain’t no such thing as a "no expansion" chamber. They all expand with pressure. While not very much, even a 2-inch thick pressure test barrel’s diameter’s enlarged with only 5 to 10 thousand ppsi so piezoelectric pressure gage will change the current going through it and record the pressure curve. Best example of this were the pressure sensors that wrapped around the barrel; they got longer as the barrel expanded.
To which Mooseman replied:
Quote:
Excuse Me ? But you are Not exactly correct. It Takes around 40,000 PSI before steel will start to expand under pressure , but it isnt even measurable except by calculation , however, the steel springs Back from the ~.00001(1 hundred thousandth of an inch) or less expansion when the drop in pressure lets it go back to the original size.
If one really believes it takes around 40,000 psi of chamber pressure before a steel barrel starts to expand, maybe they should challenge Oehler Research Inc. as to the credibility of their Model 43 Personal Ballistics System. Based on this premise, the Model 43 should not be able to be used on any barrel used for ammunition producing peak pressures lower than 40,000 psi.
According to Oehler, their System 43's strain gages epoxied on .22 rimfire rifle barrels’ chamber area, the barrel diameter expanded enough to lengthen the strain gage sensor to register pressure down in the 24,000 psi range. And they’re also used on shotgun barrels to record lower pressures in the 11,000 psi range. The pressure waves displayed with their systems go from about zero up to peak then back down to near zero.
All of which means steel barrels expand at pressures well below even one-fourth as much as 40,000 psi; close to zero psi. Of course, they shrink back to original diameters as their elasticity limit hasn’t been exceeded. Oehler’s gage actually measures the strain on the outside of the barrel over the chamber by stretching as barrel circumference increases. The stretch is directly related to the chamber pressure by the inside and outside diameters of the barrel at the point of gage attachment. As pressure drops, the barrel circumference and gage length shortens.
i believe a barrel does expand because when ever you apply heat to metal it expands and cold contracts it. if you was to get an i.d and o.d measurement from the barrel and chamber before fireing it and then another right after fireing it the numbers won't match because the heat will expand it.had to install way to many metal sleevs into hardened crane booms . when they are cold the bushing looks like it's to small but after 30 minutes with a rosebud and putting the bushing in the deep freezer it goes right in . now taking it out is another story it has to be cut out because they are now bodybound together.so my answer is yes barrels will expand due to heat.
To which Mooseman replied:If one really believes it takes around 40,000 psi of chamber pressure before a steel barrel starts to expand, maybe they should challenge Oehler Research Inc. as to the credibility of their Model 43 Personal Ballistics System. Based on this premise, the Model 43 should not be able to be used on any barrel used for ammunition producing peak pressures lower than 40,000 psi.
According to Oehler, their System 43's strain gages epoxied on .22 rimfire rifle barrels’ chamber area, the barrel diameter expanded enough to lengthen the strain gage sensor to register pressure down in the 24,000 psi range. And they’re also used on shotgun barrels to record lower pressures in the 11,000 psi range. The pressure waves displayed with their systems go from about zero up to peak then back down to near zero.
All of which means steel barrels expand at pressures well below even one-fourth as much as 40,000 psi; close to zero psi. Of course, they shrink back to original diameters as their elasticity limit hasn’t been exceeded. Oehler’s gage actually measures the strain on the outside of the barrel over the chamber by stretching as barrel circumference increases. The stretch is directly related to the chamber pressure by the inside and outside diameters of the barrel at the point of gage attachment. As pressure drops, the barrel circumference and gage length shortens.
It's one thing to try and find the truth to your query. It's another to post asking for information.
It's completely another to then take and use the help you were given and based on information that differs from it, use it to call out those who helped.
I guess what I'm saying is there could have been a different way and you could have been more tactful in your approach. Because to some, to those who helped, it could look as if you're intentionally calling them out and making it seem like what they told you was and is a complete lie and they might not or don't know what they're talking about...That's what it looked/looks like to me anyhow.
Please don't quote him. That's the only way I can see him now. With all due respect, he seems to have no other reason for being here other than to try and start a pissing contest.
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For info purposes only, use it at your own risk. JFKimmons and G&G aren't liable for it's misuse.
The piezo is measuring pressure as an impulse thru the steel in Dynamic pressure.
It does NOT actually measure chamber expansion, just the pressure put on that chamber at a given spot as transferred and absorbed by the molecules.
By measuring fired cases from Rifles , wildcatters have used actual Micrometer readings noting that when at or EXCEEDING the 60,000 PSI chamber pressure , the brass at the pressure ring will show a .0001 to .0002 increase in diameter above 60,000 psi and at 70,000 PSI there can be a .0005 increase of brass size at the pressure ring.This leads to sticky bolts and hard to extract cases and is a warning sign to decrease powder charges to stay below the 60,000 PSI threshold. So we are talking 1-2 TEN THOUSANDTHS OF AN INCH at over 60,000 PSI divide BY 2 for 180 degree case measurement so the chamber expanded .00005 to .0001 (5 hundred-thousandths of an inch to 1 ten thousandth of an inch) at the moment of Full pressure.(Microns)
Different steels have different amounts of Fluidity and the molecules in steel have certain points of elasticity , rigidity, and strength. Different barrels like thinner shotgun barrels will act differently under lower pressures.Different Brass will act differently too due to thickness and composition...everything is relevant.
Heat and cold adds another factor into the equation of expansion and contraction of steels too. Diameter and thickness also factor in.
Most Gun steels are rated at a yield point of over 40,000 psi (where the steel starts to react to pressure) to a burst point at anywhere from 75,000 to 110,000 PSI.) They must meet ANSI /ASME standards when manufactured.
There is also a temperature rating for expansion, tempering and Melting.
I have worked with Mechanical Engineers, Machine shops, gun steels, and reloading/Load development since I was 17 years old as well as welding and engineering in the past. You seem to want to nit pick and attack several of us here on the forum for what we know and have experience at , so I will openly ask You on the forum...
What experience do YOU have working on guns, working with steel, etc. ???
You want to talk chamber expansion measurements 1/10 or smaller than the thickness of a human hair...we can talk Microns ! But to the general public or laymen...It is Insignificant !
Personally, I think it would be most appropriate if some mod other than Moose would take this opportunity to lock this thread. The point has been made and hopefully taken, but Moose is involved in the discussion and someone else should shut 'er down immediately after deleting this post of mine.
I surrender Bart,if you were posting to me about the "no expansion" I posted which should have been "non expanding" chambers.Now we know for certain that chambers expand under pressure (or would you prefer me saying "barrel"?) (I never had any doubt,but called it what everyone else does)Really tickled,happy,pleased,etc,etc,that you posted to get me straightened out.Thank you.
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Samuel
8Likes
lets talk about headspace...sorry jk
Teach
