The operative word is “yet.”  A modified patience is the key.  Rust is not necessary, (although it does complicate things sometimes), but there is nothing like the death grip of two pieces of metal that have been screwed together for 100 years or more.

My record so far is 17 days.  That was a Rolling Block carbine with the barrel in the barrel vise, an anvil tied to the action wrench, occasional applications of heat and Kroil to the receiver/barrel joint, and a good bash with a lead hammer every now and then as I passed the setup and got annoyed with it.

It was a day like any other day.  There was the setup, irritating the heck out of me like it had for over two weeks.  The anvil hung by the hardie hole six inches off the floor just as it had from the beginning.  I grabbed the lead hammer, gave the wrench handle a good bash, and the anvil dropped to the floor.  I thought for a moment that the barrel had come loose in the vise, but the top of the receiver was no longer aligned with the rear sight holes.

The receiver unscrewed the rest of the way by hand.  No rust.  I walked out the door, held the receiver to the sky, beat my chest and howled in triumph!

If you don’t have an anvil, a bucket of lead ingots from your casting setup works too.  Maybe your friend will beat my record.  Best of luck.

I fought a Martini, yup hung weight on the end of the action wench, beat on it, oiled it, on and on and on.  I took a sideways swipe at the barrel with a Dead Blow Hammer while pushing down on the Action Wench.  It popped loose.  About 1/4 of the way around the face of the Receiver was a bright shinny rub band.  All I can figure is the factory just screwed it in till it indexed.  Once it popped it unscrewed by hand.  Best of luck!  David

I've loosened stuck barrels on some of the unmentionable actions by chucking them up in the lathe and making a cut right up against the action face to relieve the tension. It works if you're not saving the barrel.

JS

Please check to see if the barrel has a left hand thread. There was a thread on the castboolits forum on rebarreling a Gras and replacing the old barrel with a new one in 45/70. If I remember right he did mention it being a left hand thread on the barrel. The earlier chassepot's were the needle fire ones if I'm right. But and there is a big but here, the thrifty French reworked the chassepot's into gras rifles. And they were all big bore single shot rifles. Your chassepot may have a model date on the left hand side of the receiver near the back end. Should be something similar like 1866 or a little later. There also may be another double date on the barrel near the breech end like 74/80 
or something similar. I got barely passing marks in high school french so am not even going to try spelling any of the arsenals that made the chassepot or gras. Heck I think I'm doing great spelling chassepot and gras. Maybe do a google search or log on to the gunboards forums and scroll down to the French rifles section and ask your question there. Hope this helps. Frank

Swamp rat ...
So basically a simplified version of Ed's Red.

Well, since we are sharing stories.  Had a #2 Rolling block that resisted heat, kroil, hammer whackin. Crushed the action. Barrel was still attached. Finally started to  mill off the action and found it had been brazed to the barrel. Ultimately saved the barrel, but lost the action.

You never know what you will find.

-06

No one has mentioned the candle trick.  Maybe its too hot but desperate times require desperate means.  Some old car/old engine enthusiasts swear by it.

Never done it but the way I understand it, is the threaded joint is heated up quite hot and then a candle or wax is melted into the joint and when cooled it allows the parts to be unscrewed.   

Anyone familiar with this method?