I want to quantify friction between a bullet and barrel to test different friction-proofing coatings and treatments.

Is there a controlled test I could do at low speeds in a lab between samples of treated copper and steel that would be theoretically applicable at velocities up to 1000 m/s? I.e., is the dynamic coefficient of friction considered constant between two materials like copper and steel up to speeds of 1000 m/s, or is there a known relationship between speed and friction that would allow extrapolation from lab-measured coefficients? And what lab tests would be suited to measuring that coefficient to high precision?

(I realize that the most obvious way to approach this problem would be empirically: i.e., just shoot the different projectiles and compare the resulting velocities. I have tried that and gotten confusing results that appear to be attributable to the sources of error in internal ballistics: in particular to the fact that different coatings are probably altering the diameter of the projectiles at the micron level, and dimensional changes can overwhelm the changes in friction, which render A-B comparisons invalid.)


I would think the friction regimes will be very different, especially for something like a gum barrel where the projectile is contained. At high speeds plastic deformation of the surface will be much more significant as well as possible chemical reactions due to the heat/energy. Therefore I wouldn't necessarily expect the coeffcients to be similar.

You could possibly could set up a test rig using a high speed touching a flat plate to test the friction at high speed outside a barrel. However, I haven't thought about the details and this would probably be difficult\expensive\dangerous to set up.

A quick google gives me this paper which supports my theory that friction would not behave consistently.


Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.