Galling or cold adhesive welding is a subject that deserves a sticky.
If you go find the engineering data at Carpenter or other stainless steel makers you will find a hierarchy of ways to prevent galling of stainless steels.
1. There are stainless steel alloys that are notorious for galling. 17-4 PH stainless is one of the worst and I call it gall-o-matic for a good reason.
If this material is running against itself the two different pieces should be of different hardnesses. Ideally you should avoid the use of a stainless steel couple where the combination of materials produce galling. When used in plier type clamps for surgical instruments 17-4 PH takes almost nothing to gall when they are super clean and have been sterilized in an autoclave. Hundreds of baby engineers learn this the hard way every year designing surgical instruments. I used to do the failure analysis on returns so I have seen a lot of it.
2. Fits between components should have a little clearance and lubrication. You cannot have much of this in surgical instruments.
3. Awful saw tooth threads should be avoided. The threads should have clean smooth flanks that will run together by hand with out grabbing.
4. Find a lube that has a very high film pressure. Do not over tighten the components.
5. Use Gall Tough or one of the Nitronic alloys like Nitronic 60 for at least one piece.
6. In the semiconductor world we used Nitronic 60 Helicoils to prevent galling along with electro-polished fasteners. We tried to get Nitronic 60 Keenserts too but the company usually wanted several milllion dollars worth of Keenserts paid for before they would run any.
7. Silver plated stainless fasteners were also used with the silver acting as lubricant
8. All titanium threaded fasteners was considered but it would have increased the cost of each machine about $6000 and we built several thousand machines in a good quarter.
>>>In addition to PFPE, Krytox grease also contains
telomers of
PTFE and in fact was designed as a liquid or grease form of PTFE.<<
Krytox is used a little in the semiconductor industry to lubricate O rings when they are installed. It costs about $35 to $75 an oz so I don't think you will want any of it. It does have a high resistance to out gassing in a vacuum. It is basically a grease of PTFE (not particles but the base material is the PTFE. I don't think it has any petroleum in it.
http://www.cartech.com/techarticles.aspx?id=1832
http://www.hpalloy.com/Alloys/wearResistant.aspx
If you have to use a stainless barrel make sure the threads are well machined with no chatter and it will thread into the receiver with out dragging.
Make sure the receiver has good threads. Use some grease, don't over tighten and use a carbon steel receiver.

BTW I hate stainless steel for all the grief it causes.