Hello all, Once again I come to my fellow gun enthusiasts for some advice. A buddy of mine just gave me a Mosin that needs a serious bit of cleaning and care. He found it in an old building that was about to get demolished. It is missing the bolt and is covered with rust. My concern is the bore, I shined a light down the bore and you can barely see the rifling through all of the corrosion. As much as I would like to get this thing back into firing condition, the bore corrosion concerns me. What are some of the finer aspects of cleaning up corrosion of this degree to the point where this is an operable rifle once again? I was thinking of submerging it in an electrolysis tank for a day to see how that fared but I am unsure. It has the Soviet crest on the receiver with the year 1933 under the crest. There is also a Triangle with an arrow in the middle. There are other markings all over the receiver but I will not be able to see what they are until I dig into this rust. Thank you for any advice you can give me. I seem to have a habit of finding rifles that need tlc which doesn't bother me except that this one is the worst one yet.