I'll be watching this thread closely to see how it works out. As a guy who works around saltwater I'm pretty familiar with the "hot wrench" (a propane torch applied to one of two surfaces that are locked down by a combination of corrosion and other factors...). I long ago began using the torch to heat - followed immediately by a penetrating spray lube and go through that routine several times before using a combination of wrench and tapping with a small hammer to free up stubborn fasteners. I've never worked on any firearm receivers so I'll be interested to see how you fare... good luck on your efforts.