Yup,
And just a few weeks ago there was an extensive thread on that very subject. Maybe one of the moderators will be kind enough to provide you with the link to it. It may be archived by now, so ...
As of fairly recently, you can buy bullets, loaded cartridges or the kit to treat your own bullets with a dry form of molybdenum disulfide. It is a surface treatment. One method I saw is by physical impregnation (it's rolled on/into the sutface). Another is a spray can that you spray on to the bullets, let dry and then load as normal. I think. 'Haven't had time to try it yet.
Any time you can reduce friction between the barrel and the bullet you are getting ahead. I once read that on average (?) 35% of the energy during the internal ballistic cycle is lost due to bullet-to-rifling friction, engraving pressure, centrifugal force, and the force spent to move the mass of the bullet itself.
A teflon barrel wouldn't last long, though, even teflon-to-teflon. Look at the bottom of your teflon cooking pans. The moly treatment works because it is embedded into the surface, not a coating, as I understand it.
[This message has been edited by sensop (edited February 27, 2000).]