Safe Practice to Consider

[Fox]

I had read once that this was related to the pressure from the primer explosion, especially with the original shotgun 209 primers causing the bullet to move prior to full ignition. Now this was in relationship to BP as opposed to smokeless, so that may negate the comment.

Powder never fully ignites before the bullet leaves the gun, that is why you need faster burning powders with shorter barrels to maintain muzzle velocity.

The case containing the powder and closed with a bullet is a pressure vessel, it is as simple as that. The ignition of the powder makes an explosion of gases that pushes the bullet out the barrel. ET1 you mention that this pressure occurs after the bullet starts moving, I don't have a problem with that, what I have a problem with is that you make it seem as though the pressure is highest as the bullet is 6in down the barrel, which would have the pressure vessel now about 3 times the original volume, which would keep a lower pressure than at original ignition.

Once you drill a hole and tap it in the barrel you do make it weaker, but not by any amount that would cause a failure let alone with a screw in place or not. The screw in place is not molecularity part of the barrel and therefore has no impact on the strength of the barrel. If the barrel were layers that the screws were holding together then maybe, but a solid piece of steel with 2 tiny holes in it does not significantly change the strength of the barrel.

[ET1]

Fox

If the strongest part of barrel rupture doesn’t convince you what is probably happening then I don’t know what will.
But that aside I would more trust what Quickload reveals than an assumption on yours or anyone’s part.
IMO Fishy Wishy nicely described what happens when powder is ignited. The quickload graph basically supports his comments.

As for who is right about threaded holes take your pick as neither side can at this moment provide some more substantial proof to back their statement. That’s why I haven’t challenged it.
Believe whatever you want to presume and good luck.

One last thing, the whole bore can be considered a temporary pressure vessel and not just the brass casing, as pressure is not limited to the casing and also occupies the bore.

One other thing the smokeless powder does a progressive burn that is why there are powders classified with different burn rates.
When the powder ignites at the bottom end it pushes anything forward including unburned powder and the burn is usually completed outside the case.

Ed

[rippin_355]

Holy pissing matches! I will post some pics of how deep the rear sight hole is and it worried me actually. As for the steel screws in a stainless barrel, they come loctited in from the factory. There was definitely a gooey substance filling the hole when removed.

[M_P]

Back to the original post - there is no doubt in my mind that drilling a blind hole in a barrel will weaken it at that location. It's simple common sense. The barrel is thinner at the hole and it would make sense that it would fail there first. But my feeble brain agrees with what Terry and Fox have said, simply putting a screw in the hole does nothing to increase the integrity of the barrel. You would need to plug weld the hole and then hope that the heat from the weld didn't affect the temper of the steel.

[Fox]

Back to the original post - there is no doubt in my mind that drilling a blind hole in a barrel will weaken it at that location. It's simple common sense. The barrel is thinner at the hole and it would make sense that it would fail there first. But my feeble brain agrees with what Terry and Fox have said, simply putting a screw in the hole does nothing to increase the integrity of the barrel. You would need to plug weld the hole and then hope that the heat from the weld didn't affect the temper of the steel.

You would have to weld the barrel which would have to get the steel over the phase change temperature of the steel (depending on the carbon content this is around 1495C) then temper the steel to get the proper molecular structure back into the barrel.

https://www.google.ca/search?q=steel...ml%3B750%3B543

The fact is that the hole will make it weaker, but a screw will do nothing to make it stronger.

The reason sights are either mounted on the barrel or on the receiver is because the part that has to be the strongest and remain the strongest is the chamber area, this is why this area is so much larger that the barrel and tapers down (unless you have a bull barrel) to the barrel diameter to the length of the barrel.

The pressure is not highest 6in down the barrel it is at the chamber.

rippin - they would put thread locker in there to keep the screws in so that they did not fall out, the hot and cold cycles of a barrel are insane and those changes with dissimilar metals will cause loose fits in the threaded holes (think aluminum and copper wiring together). This threadlocker is also a barrier for moisture and therefore galvanic reaction as well, although the nickel and chromium content of most stainless does not have enough of a charge difference to react readily with steel. Holes in the barrel do not look nice, that is why most companies plug them, plus they hold water which will rust the non-stainless barrels.

Believe it or not, if your joints are too clean and your metals are too close to the same you can weld them together simply by putting them together, this is why you use 2 different classes of stainless for the parts and the fasteners when you install super clean stainless components.

I do this stuff for a living.

[Big Jack]

I don't know about this thread....

What is the point. If you blow the barrel it makes no difference whether a screw hole is filled or not.

That 10ml is proofed to 109,000 PSI. The fact that pressure went over that makes the point of filled screw holes kind of moot.

[jaycee]

I don't know about this thread....

What is the point. If you blow the barrel it makes no difference whether a screw hole is filled or not.

That 10ml is proofed to 109,000 PSI. The fact that pressure went over that makes the point of filled screw holes kind of moot.

You've got that right!

[ET1]

Fox

Now I have a problem with your theory and only need to ask one question.

You are fixated on the powder being completely burned inside the casing and that max pressure starts there. If that were true then Boyles Law for pressure being inversely proportional to volumetric space would have the pressure 6” into the barrel greatly reduced. Yet we know if the bullet was stopped at 6” from the chamber the barrel would rupture.

So my question is where did this kind of pressure originate from that was sufficient enough to rupture the barrel that has a high tensile strength?

Ed

[G.S.]

As stated before, installing the screw will not increase the structural integrity of the threaded hole in barrel. The hole should be plugged for corrosion prevention reasons.

The barrel is designed, tested and certified for its intended service life (usually unlimited) when operated within the design parameters specified by the manufacturer. Operating outside the so-called “design envelope” might result in failure, which will initiate at the “weakest link” of the barrel structure.

Boyle’s law relates to ideal gas transformations at constant temperature, very slow speeds, constant mass, and without energy transfer (within a “closed” system). Which makes it not applicable to the thermodynamic process that occurs inside the barrel.

[Fishy Wishy]

Fishy Wishy

Tell you what read B31.3 of the ASME Code under Severe Cyclic Pressure Piping and tell me what it visually allows for surface porosity. I know that the procedure I'm required to use for dye checking has zero tolerance for even the smallest porosity for B31.3 Severe Cycling. Wonder why.

Any threaded area is considered having sharp stress risers and where accessible are usually checked with Dye or Mag inspection if NDT is required especially in-service components. You can argue that point with CSNDT who trains inspectors for CGSB certifications.
I know as I hold Level-2 RT-MPI-LPI along with Level-1 UT CGSB certifications.


Ed

I'm not experienced with B31.1 Severe Cyclic Loading. I am experienced with Sect I and VIII.

I currently hold none of those tickets...I did receive training and performed RT, MT, PT and had started UT training. I had finished my CEDO accreditation before I left NDE. I know a number of Level 3s in UT, RT, MT & PT in both GGSB and ASNT accreditations.

But this isn't a determination of NDE...this is understanding strength of materials and design.

The direction of the threads in the hole do not create a stress riser in the direction of the greatest stress.

A plug will not reinforce the barrel.

In a failure the barrel will fail in the weakest location...the hole definitely is going to create the weakest point so of course it will tear/splits there.

FW