I've got several ML's that came to me with pitted and rusted barrels and after some elbow grease and bore polishing they all shoot really pretty well and some shoot just as well as anything including new.
I've been laboring on an 50 cal Cabelas/Investarms Trade rifle that I picked up cheap butwith a really terrible bore. Since, I've got it shooting 5-6" groups from locked bench at 100 yards. I think with some more polishing I can squeak a little better accuracy out of it.
I'm with you though, I can't stand to see a neglected arm.[

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I would hang on to the barrel. You have it and you know it's a good shooting barrel. Perhaps you may find a time that you would rather have a not so perfect barrel on the rifle.
Like if you loan it out to someone or for training a new shooter or if you are going to hunt in poor weather.
M2C,
Tahquamenon