Finaly a ultrasonic cleaner that is big enough - Hornady 110 Volt 9L Sonic Cleaner Hot Tub

If you haven't tried an ultrasonic cleaner you're missing the boat. I have a smaller Hornady unit that is great on small parts but you can't fit whole guns in it. This one you can and it doesn't cost a million dollars. It's super important that the cleaner heat the fluid. Why? Not so much for the cleaning aspect, although I'm sure that helps a lot, It's so it drys. You really don't want water on or in your gun. The parts are usually too hot to touch when they come out so they dry off really well and pretty fast. If you have compressed air, so much the better. Get as much water off as you can and then spray it down with a WD40 like product and you're good to go.

I was able to clean a totally gunked in cosmoline Yugo M48 Mauser. It was so bad that when you pulled the trigger, the striker oozed forward. It was almost unclean-able with a tooth brush and solvent. The ultrasonic tank with the appropriate detergent worked a miracle.