Ron,
It sounds like you have one of the very worst stuck nipples that can be found. Believe me, I have sympathy as I've had to get out a dozen or more like that in the past at NSSA National Shoots.
Good Cheer had some excellent advice in his post above that I agree with completely. If that still doesn't work, cub45 is absolutely correct about using a fine tip flame.
SOME times it is helpful to apply some force to the nipple IF you have a substantial and correct fitting nipple wrench or socket that fits very well and rather tight. After you place either tight fitting nipple or socket on the nipple, you smack the wrench or socket with a wood, copper or lead mallet. This does not work all the time, though it works enough to try it.
With a really bad stuck nipple, it may take days before it loosens up when not using heat or cutting or drilling out the old nipple.
When I got stuck nipples out at the NSSA National Championship shoots, I only had 2-3 days at most to do it and sometimes only hours to get them out. Most of the worst ones were either original steel nipples that had been in the musket or over 100 years or steel ones that had been fired MANY shots through them and never been taken out of the muskets.
I bought nipple wrenches made by one of the NSSA shooters who really made good tight fitting ones and were made from quality steel and correctly hardened and annealed. They were not HC/PC in shape, having been made from drill rod with a hole drilled through them and another smaller diameter rod through the hole (to form a T handle) and just peened on each end to keep it from coming out, but they were incredibly tough.
I had what may be described as escalation of force techniques that started out with the lowest amount of force and worked upwards with more force as the list goes on. In the early years, I used penetrating oil and let it soak in for a few hours or few days, depending on the time I had before the shooter required the musket back. As better penetrating oils or PB Blaster came out, I used them. This was also in the time before one could get small cans of compressed air to cool or “freeze” the nipple.
1. Try tightening the nipple more or at least putting some force in a clockwise direction with one of those great quality nipple wrenches. Then with pressure holding down on the wrench, try to quickly "snap" loosen the nipples. This usually only worked on the Bronze/Ampco nipples, though.
2. Take the barrel off the musket and clamp it securely in a well padded vise. Take the quality nipple wrench (or good fitting socket) and place it on the nipple all the way on. Give it a couple good whacks on the end of the wrench or socket with a wood, plastic, copper or lead mallet. Now you can’t go overboard on this or you MAY wind up hammer welding the metal into the threads and especially with Ampco nipples. The impact sometimes loosened a stuck nipple.
3. Heat the nipple only with a fine tipped torch as cub45 mentioned. I made heat shields out of sheet brass to use when I did that (along with other such heat shields when I had to heat and rebend a Musket Hammer).
4. My last resort was to use a Dumore Handy Grinder with carbide cutting burs to cut the top of the nipple off and cut down into the body of the nipple below the surface of the barrel. That tool is described as “A Dremel Tool on Steroids.” The combination of cutting well down into the nipple and the vibration always allowed me to get the nipple out, though you have to be exceptionally careful not to cut into the threads of the barrel metal. I frequently used Cold Blue inside the nipple to ensure I did not cut into the threads, as that stuff would highlight even the very edge of barrel threads. I found that by cutting a sort of thick screw driver slot in the base of the nipple and a screwdriver I ground to shape with a THICK blade to do it, allowed me to get the nipples out easier than using “Easy Outs.”
The absolute worst case of a stuck nipple and the highest case of stress doing it, came one year at the Nationals on the night before the first day’s shooting. (We always got there one day early to set up the booth and then I set up my little “gun working area” in the back.) That night around 7:00 PM, a shooter showed up with a GORGEOUS original M1863 Springfield that had the nipple stuck in place. My jaw dropped when I saw it as it should have been in a museum and not on the firing line.
He told me he had bought it a few months before, but did not trust any gunsmith in Minnesota to get the nipple out and that’s why he saved it for me to do it, as I had removed stuck nipples for him and other shooters at past shoots. Of course I was flattered, but when he told me he needed it the next morning to shoot, I was not sure it could be done. I also did not want to leave any kind of mark on that superb condition original musket.
In those days, my “work bench” was a small wood indoor furniture table and my vise was a small screw clamp on type. Oh how I wanted my large work bench and vise for THAT gun as well as some others we worked on at the Nationals!! (Years later when we moved into the NSSA owned buildings, we built a substantial work bench with a larger vise in the rear of our booth.)
It took me about 2 ½ hours to get that nipple out using both heat and then cutting into the nipple body to get it out as I went VERY cautious on it and stopping frequently to remain in sharp focus. Of course a number of people also came by to “Kibitz” while I was doing it, to see “how it was coming along,” so that increased the already high state of stress. When I finally got the nipple out with not a single mark on the gun, it was like a Giant Weight had been lifted from my shoulders. The Owner showed up again about 15 minutes later after I had calmed down a good deal. Grin. Of course he was happy, but he was rather nonchalant about it as he had expected me to do it that well. Other very experienced shooters, who had been around while I was doing it, were really surprised at his reaction. A few of them talked to the owner to explain how difficult it was to do it the next day. So the day after that and after he had shot it in competition, the Owner came back and thanked me profusely. I told him I was just Very Glad and Very Relieved it came out when it did and thanked the Good Lord for His help on me doing it.
Gus