Mirror Polishing Compression Tubes - The Evidence

[Hsing-ee]

In the first frenzy of springer airgun tuning the sage advice was to mirror-polish the walls of the compression tube with a mild abrasive like Solvol Autosol. I've done this to a large number of springers, and it is a boring process both doing it and cleaning up the resulting mess.

I think I might even have kept in in my old 'advice thread' 'Tuning the Older Springer'.

This technique was advised in the days when most piston washers were made of leather; a few like the BSA and the Sussex Armoury, used 'O' rings while Feinwerkbau was well ahead with a nylon head (Sport) and steel piston rings (150/300 series). Maybe leather needs mirror-finish more than nylon or other plastics, I don't know. There are some who say you need some cross-hatched roughness on the compression cylinder wall to hold lubricant, but it must be pretty poor lubricant that can't do the job with mirror finish, it should work as roughness will still be there at the microscopic level even if it looks perfect and shiny.

My question is; given the strength of the spring and the fit of the washer, does a mirror-finish make ANY difference in real terms to the efficiency of the power stroke? I have a feeling that it makes no difference whatsoever and that we have been wasting our time for years. There is also the possibility that after the polishing it is uneven, which if it DOES have an effect, won't help with consistency.

Has anyone done a before and after friction experiment? I know that this might be different from when the spring is pushing the piston and there's a massive head of high pressure air in front of it pressing the washer against the walls, but I bet a simple test with weights and a timer would show the difference between mirror and factory finish is 3/16ths of sweet FA.

Your thoughts please genklemens?