I worked on an heirloom gun today, mentioned it in another thread. My best friend's wife's Grandpa is the owner, but it will be going to best friend's wife when he passes. Their cat tried to mark it's ownership and therefore the whole thing was covered in urine crystals, seized up, corroded, and smelled of ammonia. The ONLY moving parts that actually moved was the barrel release lever (barely) and the shell ejector. So I tore this thing down until it bore a strong resemblance to the exploded diagram I was working from, vacuum sealed the stock in a baking soda solution to neutralize the cat odor, and scrubbed all the uric salt crystals and rust out of this gun. The barrel got polished inside due to a large amount of surface rust, especially in the chamber. The stock has cracked and has been epoxied once, will need at least one more treatment before it can be trusted to hold. The butt plate still smells like cat essence, so it is getting a nice soak in baking soda solution at the current. The only parts I didn't have off of this gun were the ejector and the bead. Below are some photos I took as I was working on the gun, I was sending them to my friend. Most are post-cleaning as I didn't think to take before pictures as he knew the condition going in. Funny thing is, I have an identical gun (albeit in better shape) and at least I am confident now that I can fix anything that should ever go wrong with it.
And the exploded diagram, complete with labels (I couldn't find this anywhere so I wanted to upload it so it will show up in google searches for others).
He picked it up last night, was very happy with it. Glad he brought it to me instead of a gunsmith-- would have probably paid more than the gun was worth to get it back up to snuff.