Quote Originally Posted by NickG View Post
I tried delrin for o ring piston heads and after time it broke up, cant say if this was due to temperature or the impact.
I once deliberately crashed a lump of acetal into a cylinder end cap at 15.51 M/s, Nick, and it did not show any signs of damage. The fastest crash I've recorded on a second forward piston stroke is nearer 9 M/s, so it should withstand one such crash, and certainly a more 'normal' hard landing ~6 M/s, but multiple collisions may cause cumulative damage.

High temperature would I assume soften the surface and make it less prone to breakage, so impact damage seems the more likely culprit.