Chamber Rust (M96 Swedish Mauser)

[Patrick Chadwick]

"There may be trouble ahead...."

It sounds as if someone either fired black powder in the rifle (BP-loaded blank cartridge, maybe) and didn't clean it - black powder residue is actually white when dry - or used some aqueous chemical agent, and didn't clean out that either. The effect is more or less the same.

Whichever is the actual situation, I must tell you that the worst scenario is
1) that the chamber is so deeply pitted that a cartridge cannot be extracted. If it is not feasible to recut the chamber, then the barrel is scrap.
2) Second worst is that it is not pitted that deeply - cases will extract, but the pitting causes a bump to appear where the cartridge expands to fill the pit. I have a BP rifle like that, and it's a candidate for the scrap heap, because the cases are going to break up pretty quickly around the bump, and they are expensive.
3) Third worse is that cases extract, but you see a blemish. In this case, the rifle is usable, but examine the blemished area after each firing for signs of case strain. 6.5x55 cases are cheap enough that you should simply bin any cases that look overstressed.
4) If you don't even see a blemish after firing, I would imagine that the rifle is usable.

Which situation have you got? To decide that, the rust must be removed. You have suspected quite rightly that rust is bulkier than the original steel, so the rust spot is narrowing the chamber, and you must NOT fire the rifle with the rust still in the chamber. It is advisable to take the action out of the stock, so that you can treat it without worrying about damaging other surfaces.

First step: Plain mechanical cleaning. Use the finest wire wool you can get, twiddle a small hank around a bore cleaning brush mounted on a (preferably brass) cleaning rod. The brush is just there to hold the wire wool, so size is not critical.

DO NOT BE TEMPTED TO GET THE JOB DONE QUICKLY BY USING AN ELECTRIC DRILL TO ROTATE THE ROD

I apologize for shouting, but I have seen several rifles that have been ruined in this way. There is nothing like a wildly rotating electric drill for scoring a bore or a chamber! In fact, it would be better not to rotate the rod at all, but to push it in and out until you feel that your arm is dropping off.

Every now and again, take a break, clean the chamber, and take a look. In a perfect chamber you will be able to see the rifling reflected in the wall. That is probably not the case here, but you will, with a little practice, be able to concentrate your view on the chamber wall rather than looking down the barrel. Eventually, you will decide that the chamber wall appears to be as clean as you are ever going to get it with this method. But we are not finished yet.

More later today. In the meantime, you can get started...

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