All good advice here, especially Neds, about pretending you never heard about it being a problem.
He also got it all right about it being a very very bad idea to have the same stainless steels with THE SAME HARDNESS sliding together. JiminCa is spot on about 300 Series stainlesses being the worst of the pack, but its not used in guns to my knowledge. The 400 series of stainlesses used in guns are heat treatable and of martensitic structure (ie. magnetic), thats why they can rust. Their rusting charecteristics are also affected by the hardness you treat them to. The harder you treat them , the more corrosion resistant they become.
SO long as you have the two similar stainless steels at different hardness levels and use good lube with adequate running clearance you will have no problems. Good thing slides and frames are not the same hardness.
Lube and running clearance can be best appreciated when one knows the mechanics of galling. Galling occurs when as everyone knows, two similar pieces of steel come into contact with each other under dynamic conditions. Machining of steel always leaves high and low spots in the finish, we refer to the finish in RMS (root means squared ) numbers. so an RMS finish of 125 is coarser than a RMS finish of 32. That means a finish of RMS 125 has higher peaks and valleys in the finish than say a RMS of 32. When two pieces of steel slide against each other under marginal or nonexistent lubrication conditions they can make contact. It is this contact that can create the problems. When the high spots of the two pieces meet and touch, sometimes they "weld together". In a firearm, the slide moves and the frame is stationary. When this welding has taken place, the slide continues to move, causing one of the high spots to rip loose from its original piece and is now stuck on the other piece, reducing clearance between the two pieces at that point, and creating an even higher sopt on the other one which allows for even more interference and galling to take place. It will continue in this manner intil the two parts sieze and can no longer slide due to no clearance at the built up area.
When the heat treat of the two steels is different enough, probably in the range of 10 or more points on the Rc scale, their affinity to "weld" together is greatly reduced. Also, the smoother the finish, the less peaks and valleys to worry about.
The whole idea behind lubrication is to keep the parts from actually touching. This goes for all machinery, not just guns. Modern gun lubes will all do a creditable job of handling the loads imposed on them. All they have to do is be able to withstand the hydrodynamic, or hydrostatic loads placed on them without "squeezing" out. When lubes work propperly, they carry the load between the two parts preventing the parts from actually making contact, also known as boundary film lubrication.
What happens to lubes in a gun under microscopic conditions is up for debate, but this is my take on it. Remember the peaks and valleys? I think the valleys act as a sort of lube resevoir, both on the slide and frame. As peaks cross valleys they pick up a bit of the lube and are floated over the other peaks. As the slide moves back and forth it replentishes the valleys in the two pieces.
If I remember more, ill edit the post , but this it in a nutshell.
