Quote Originally Posted by evert View Post
Its not only expasion/contraction, it is seal hardness. Harder (colder) seals often have less friction.
Yes I agree that very cold seals tend to behave like metallic piston rings. Your idea to investigate velocity changes induced by variable air temperature using the FWB 300 is very good. Should give a very good indication of the effect of low ambient air temperature in front of the piston just before the gun is shot, without having to account for the plastic nature of the seal.