[Despoiler]

My Mossberg 500 has been growing something on the barrel. Actually the growth is at the base of the barrel right where the collar that slides into the receiver meets the barrel. I have cleaned the gun numerous times and after a couple of weeks the white powdery stuff shows up again. The substance wipes right off and doesn’t seem to be harming anything but I was wondering what it is.

The gun is stored is stored in a safe in my garage. I have desiccant crystals in the safe and I keep them fresh. None of the other guns in the safe have anything like it on them nor does the Mossberg have this stuff anywhere else on it. I am thinking that is was some type of flux that was used to connect the barrel to the collar that is causing the problem, have you guys any ideas what it is or how I can get it to stop?

 

[gunmanguns]

one of the same

i have the same stuff on my 10/22 krinker plinker [ak47] upgrade?i also wonder what it is.

 

[jerry]

Almost sounds like a dissimilar metal issue. The reciever is aluminum and the barrel is steel. Typically in this situation there has to be an electrical charge.

http://www.assda.asn.au/asp/index.asp?pgid=18533

You would have to meet some stringent criteria for this to happen. However your geography may have something to do with it, near an ocean. Throw in a bit of static electricity, viola.

 

[joeshooter]

If there's a metal finish sometimes a thin layer of oil helps with it. I'm not sure what it is, but that usually keeps it off of my guns. It's caused by moisture, try getting some Break Free to oil it. That oil is the best stuff in the world. It was designed for beach landings where the firearm might be exposed to salt water. Check your local outfitter for it. Sounds like Jerry knows what he's talking about though.

 

[Mooseman684]

The white powder is Aluminum oxide from an aluminum part that is corroding,due to bare metal being exposed to something like salt air or it could be from nitrates in powder residue. I strongly suggest having the gun examined by a gunsmith and replacing the corroding part(s), as this sort of corrosion can weaken a part quickly and cause a failure! The Aluminum parts should be prepped,etched, and then coated with aluminum Black or a clear sealant, or something similar.
Rich

 

[Despoiler]

No I don't think that is the problem, you're correct that the receiver is aluminum and the barrel is steel but this is happening at the base of the barrel, in my manual they call the collar the "barrel extension", it is right where the chamber is on the barrel assembly. Both the barrel and the " barrel extension" are steel, and the stuff is coming out of where those two pieces meet. They are both steel, I used a magnet. Like I said earlier it doesn't seem to do anything to the gun, and it just wipes right off but it always comes back. I have tried oiling it with Break Free and that doesn't help either. I do not really think it is a big deal, but I was just wondering what this stuff was. As far as being exposed to salt water, I don't so, I have not stormed any beaches lately with it.

 

[Mooseman684]

I looked at my barrel...The Barrel extension is a different metal than the barrel and if you hold it under a very bright light you can see the difference in bluing....yes they are both steel. You are getting white powder out of the joint of the barrel and extension, not between the barrel and receiver ... Thank goodness for that ! What kind of lube are you using ??? anything with say a dry teflon ??? Need more Input ! You have removed the barrel and looked at the mating surfaces I hope...you may need to soak that end of the barrel in Mineral spirits and then air blast it clean to get whatever it is that is in that joint out and then apply a very light oil to that joint and air blast it as well after it soaks in. That is my suggestion,I hope it helps !:right:
Rich

 

[dogman]

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[Bull Barrel]

I get an odd whitish residue when I use "Bore Scrubber" type aeresol cleaners--might be them breaking down the (break Free) teflon in the lube I use. It wipes off. As long as it isn't aluminum oxide from an electolytic reaction of disimilar metals you are probably okay.

 

[Ctwo]

Now I think I've seen that too. I'm going to have to check it again. Mine is new with less than 100 shells through it on one outing at the range. I just wiped it down after with outers gun oil on my barrel snake and oil soaked flannel rag. Then it sits in a foam lined plastic case.

If I see anything, I'll post pictures. I think I remember seeing it on the barrel where the chamber flares out, there was a step and the white stuff was in that step...

 

[Ctwo]

just so we know, just in front of the breech on the barrel where the step is...

This is just an image I found online

 

[Ctwo]

yep, there was little bit more there, more on the bottom where I could not get to very well between the BBL and Mag.

Wiped it off and oiled the area liberally...