M39 fouling

Danus ex · Aug 13, 2008

I've fired approximately 400 rounds (Bulgarian surplus) through my unissued Finnish M39. I've done this over about six range sessions and after each one, I Windex the bore and spray/wipe down the bolt face at the range. When I get home, I disassemble the rifle and apply Wipe-out foaming bore cleaner, come back when convenient (after a few hours) and patch out the foam. I'll oil it then too if I don't plan to shoot it for a while.

After my last range session, I did my usual routine and found that there was still some fouling in there, visible only from the muzzle end. This fouling starts about 3–4" from the crown. I broke out the brass brush and ran it through the barrel a few times, put some brake cleaner on a patch, and pushed the patch through--pitch black!

I've repeated this process about ten times and every patch after the brushing comes out almost totally black. I'm a tad worried, as I owned an M28 (which I never shot) that had pitting/bad fouling that also began about 3-4" from the crown and was only visible from the muzzle end. So:

What's going on?
What is this fouling?
Is it a problem?
What can I do about it?
Why don't I have this problem with my Garand, MAS 36, 98/29, 91/30, etc.?

aka108 · Aug 13, 2008

I've found that once the bore gets its initial cleaning that letting solvent set in the bore for 2 or 3 days will get almost as much stuff out as the first cleaning did. Takes time for it to do its job.

jjohnson · Aug 13, 2008

Ammonia

One thing that may compound things a little here is that ammonia will cause brass to turn black - try leaving a bronze brush in your windex awhile and see what happens. Some of what you're seeing may be from the reaction between the copper and the ammonia. :scrutiny:

I don't think that's all that's going on here. I'll watch with interest as those folks who use a lot of corrosive primers post more.

Danus ex · Aug 13, 2008

Resolved...for now

I removed the fouling. It took a lot of elbow grease and a few hours with GM Top Engine Cleaner. Not my favorite trick in the book, but there's no visible fouling anymore. Took forever to patch out clean.

The real test will be how it looks after I shoot and clean it next time.

Bezoar · Aug 13, 2008

actually the real test is in a few days. no doubt you have oiled and put the rifle away. tomorrow or the day after, take the rifle out.
push a clean patch through the barrel, and if you think its nice and clean ..
run a patch soaked in hoppes 9 thorugh and let it soak for a few minutes, and run a clean dry patch through and tell us how that patch looks.

i had to do a second all day cleaning sesson on my 91/30 today. so far ive used 6 ounces of bult cleaning patches. i think my trouble was that the shoulder area in the chamber was traping grime. but right now oiled, solvent, and dry patches come out unchanged.
nothing worse then having a solvent patch followed by half a dozen dry patches come out clean only to have your final "put it away" oil patch come out looking like you wiped a sewer pipe out with it.

nicholst55 · Aug 14, 2008

Correct me if I'm wrong, but isn't Wipe Out intended to be left in the bore overnight? I would think that coming back to finish cleaning after only a few hours would be counterproductive.

Cosmoline · Aug 14, 2008

Your bulgy surplus is probably .311" out of a .310" m39 barrel.

stubbicatt · Aug 14, 2008

Anymore with the Mosin Nagants I use a cup full of hot water and Ballistol. Dip a bore brush in the solution and scrub the barrel. Dip again, scrub again. Keep this up until no black smuts come off the brush into the water. Then dry patch. It seems to work well, and is less effort than some other methods.

KI.W. · Aug 14, 2008

Maybe there is 7,85 barrel.

M39 fouling

Danus ex

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aka108

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jjohnson

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Danus ex

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Bezoar

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nicholst55

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Cosmoline

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stubbicatt

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KI.W.

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