No4 Rusty Chamber advice please.

Another novice question I'm afraid!.

Just got LB No4 Mk1* which was recently reproofed(It did not appear to have been cleaned for a while though). Took it to Zero and immediatley noticed cases seemed to be stretched(crazed) about 10mm from the rim for about 3mm, and also extraction a bit stiff. On closer inspection, the inside of the chamber is rusty at this point and for about 15mm further into the chamber, so it appears that the "crazing" is the imprint from the very finely pitted rusty area onto the brass. Not sure why just this portion of the chamber has rusted, as the rest looks fine, as does the barrel.

The question is, should I leave the rust and just use it "as is", or try and polish it out. Obviously polishing it out will increase the chamber dimensions and not sure if this might make things worse.
I'm sure this must have been covered here before, but a search did not reveal much.
Any advice appreciated.
jss

If you have only just bought it, why not take it back? Plenty of excellent No 4s out there. Any dealer with a reputation to protect would not quibble.

Obviously, the best bet would be to take it back to the seller and exchange it. If this is not possible, convenient, or you are a bit attached to the rifle or got a real good deal on it, then a LIGHT polishing should clean up your problem a bit.

First of all, the rusting does not appear to be too bad if you can extract the fired cases without a lot of effort. The key here is to go SLOW and CAREFUL.

I would first try some EXTRA FINE steel wool. You could take a 3/8 inch wood dowel about 10 inches long, put a slit in it, and use an electric drill AT SLOW SPEED. Do not use oil to start with, and do not extend the dowel and steel wool down the chamber any more than necessary. This should clean up a lot of the fine surface rust. I would also put a cleaning patch about 4 inches or so into the barrel from the chamber end to catch any rust or steel wool that might come off the cleaning tool. It should not take more than a minute, then clean and inspect the chamber. If it looks good, then try firing a few rounds.

CAUTION - MAKE SURE YOU REMOVE THE CLEANING PATCH IN THE BORE.

If the problem still persists, then you can use the same 3/8 wood dowel with the slit in it, and find some 600 or 800 grit emery cloth. This comes in 1 inch wide rolls, and you only need a couple of inches. Cut a piece about 2 inches long, thread it through the slit, then roll it so that it will enter the chamber. Again, SLOW and CAREFUL and do not run the drill at high speed.

This should not change the chamber dimensions too much if you watch what you are doing.
.

As a UK dealer myself, I'd advise you to take the rifle back and ask the vendor to sort it out or replace the rifle.

As the other have mentioned, in fact this isn't a major problem, and polishing usually solves the problem. I don't think you have to worry about enlarging the chamber, just through the vigorous application of a wire brush or some wire wool.

I agree with Rob and Thunderbox. Take it back. Additionally, I would worry about buying anything further from a dealer that sells rusty rifles.

Thanks for the advice gentlemen. I got the rifle at trade price in px for another duff one. This one is all matching (Bantam Stock unfortunatly), so I'll try a bit more polishing. I have managed to polish some of it away with metal polish, but I'll try fine wire wool and see how that goes.
I had a good look at the chamber before purchase, as I have been caught before, but the red color of the rust was not apparent. I think cleaning it has removed a covering layer exposing the rust underneath, and possibly revealing the pitting.

Mount one of your fired cases on a mandrel by whatever means is easy but strong and use the assembly as a lap along with a fine grit polishing paste. If there's no rust in the neck area of the chamber you might want to cut off that part of the case. Works well if you're careful.

But whatever you do, remember that to remove the corrosion, you WILL be making the chamber oversize