I remember doing that when I picked up my 6.5mm Swede Mauser. The guts were so thick with grease I had to use a sharpened popsickle stick (no metal on metal) to scape off the black crud.

I was pretty relieved to find matching numbers down inside when I had it all shiny and clean on the newspaper.

Just don't be one of those guys that "Bubba-izes" thier C&R firearm.

Here's a kick-ass tutorial site on Milsurp Rifles and their stripping & assembly.

http://www.surplusrifle.com/mauserswedish/boltdisassembly/index.asp