I've got a well worn in Model 70 that I'd like to have coated for rust resistance, but I'm worried that the coating will build up on the metal and make the bolt harder to operate. Are there any coatings that can preserve a gun's smoothness?

You mean like chromium or titanium?

Hard Chrome , or ( TIN ) titanium nitride coating . It's almost indestructible either way .

Milling machine ways are hard chromed or TIN coated and we all know what they are subjected to.

Shoot Straight Know Your Target . ...

Do a search on Melonite. It is very slick and leaves a 70 Rc hardness. I use it on barrels on my BR rifles. It does not build up, it treats the metal.
Butch

Thanks guys, I was thinking of cerakoting this rifle, but looking at the specs I'm worried about the thickness of the coating.