I am curious about calculating stress at various points along a barrel as a bullet is being fired through it. The interference fit (press/friction fit) equations immediately come to mind, but I am wondering if these equations are appropriate to use because of:

(i) The non-linear pressure curve of the gas behind a fired bullet

(ii) The bullet is moving through the barrel (dynamic system)

Here is a link to some interfernce fit equations I'm refering to, http://www.engineersedge.com/calculators/machine-design/press-fit/press-fit-equations.htm

Any pointers?


1 Answer 1


Indeed, you can use the same equations for calculating the stresses, as the barrel essentially is a thick walled pipe with internal pressure.

Looking at the equations you linked: (7) "Radial Stress Casued by axial force" (8) "Circumferential Stress Caused by Axial force" are the right ones. (there seems to be a mistake though: the correct term for (8) would be "Circumferential Stress Caused by internal pressure"

The nonlinearity of the pressure: the pressure will be the highest at the chamber. Assuming an even wall thickness, check the stresses here and you are ok. In case of changing barrel outer diameter, you shuld look for benchmark pressure curves, and check the stresses at multiple locations along the barrel.

Dynamics: in my opinion this concerns the fatigue life of the barrel. To calculate the lifetime in terms of number of shots fired and survival probability, you will need the Haigh-diagram of the chosen material. But I believe the wear will be the limiting factor.

edit: this paper seems to be dealing with the same issue: http://www.slideshare.net/JoshuaRicci/design-of-a-rifle-barrel

  • $\begingroup$ :D I can't wait to blow my fathers mind. Thank you. $\endgroup$
    – Grant
    Aug 30, 2016 at 18:25

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