The barrel fails as result of the force of the second round colliding with the first bullet not from pressure resulting from fire normal round (internal ballistics). These are technically refereed to as obstructions.

Cylinder failures are always the result of over pressure, barrel ruptures are typically the result of obstructions.

Peak pressure in 38 special (and most other strait wall handgun cartridges) occur before the bullet even leaves the cartridge.

Even when slower powders such as 4227 is used in even the largest of handgun cartridges such as the 460 S&W or 500 S&W and operate at twice the pressure of 357, the bullets still have not left the brass before the peak pressure has been reached.

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Ruggy

When one bullet rams into another bullet and there is no where for it to go, that is pressure anyway you look at it. The gases are still pushing and do so until the bullet exists the bore or they find another escape route, whether it is peak pressure or not.

Rosewood

yes

But not from powder burning but as result of a change in momentum and surely would not be measured in psi.

The pressure dissipates through the BC gap and there is no escalation of pressure. The pressure is well below design as the peak occurred while the bullet was still in the brass.

Obstructions damage the barrels in revolvers not the cylinder, Cylinders are damaged over pressure in the cylinder under ALL conditions.

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Ruggy

Then why do you get more velocity with a longer barrel? It is still being accelerated.

Velocity is a function of total pressure under the curve
A longer barrel increase the time the bullet has pressure applied and area under that curve.

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Ruggy

Exactly, and the pressure isn't all gone out the GAP.

The generated gas pressure in the system is the same on all surfaces and will dissipate out the BC gap.
The very nature of pressured systems is equalization.

Once the bullet stops at the obstruction there are no outside forces on the gas to prevent it from equalizing with atmosphere (the pressure outside the BC Gap).

If you think otherwise were does it go?

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Ruggy

What would force be measured in? Pounds per square inch is force over area. The total force of one bullet impacting another can be expressed in pounds per square inch. Total force divided by the surface area squared where they are touching is psi.

Most labs would most likely use joules as the total amount of energy in collision studies, as usually the are multiple contributing forces acting in concert.

In simulation software such as Solid Works (which I speculate S&W and most Firearms companies are using to perform stress analysis and prototyping) the output is typically a thermodynamic expression.

When I return to my office I will add some technical resource references on internal ballistics and terminal ballistics for those interested at the real science.

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Ruggy

But my statement is still accurate regardless of "most labs would use".

Rosewood

Thinking like this is why SAAMI exists, and why their recommended max pressures are so so low . . .