I agree with
@desi23's assessment.
@MacShay's rifle is from about 1970.
I would consider removing the barrel from the stock. I am not sure, but the nose piece may be threaded into the barrel. Those two screws should be removed. The pins that are in the diamond inlays hold the stock to the barrel. Those pins will have to be removed to separate the barrel from the stock. I do not see pins holding the thimbles in the stock. Are the thimbles threaded into the barrel? If the thimbles are threaded into the barrel, these will have to be removed.
I've acquired an old flintlock muzzleloader (seller thinks it is still loaded) and I tend to agree since the ramrod won't go all the way in. There is no powder in the pan and I've removed the flint. I've tried two different ball pullers with no result. The barrel is so rusted I can't seem to find any markings so not sure what kind it is. Have not disassembled it yet but thinking should take the barrel out and remove the breech plug to unload. I do not have much experience with black powder guns so am hesitant to take apart. Have seen other posts where people have used CO2 extractors to blow the charge out and even one where the fellow used a long drill bit to tear the ball up. The barrel looks to be around 35 inches long and likely it is .45 caliber. So I'm looking for some advice on this. I'll post some pictures tomorrow.
MacShay did not tell us if he poured a penetrating lubricant (Kroil, ATF and acetone, or any other penetrating oil) before trying the ball pullers. What residue was pulled out when the puller was removed? Was it lead or wood from the broken ramrod? Did the ball puller thread into the ball? Being a flint lock rifle, does this rifle have a vent liner? It is hard to tell from the lock picture. Do you now have a hole through the ball? What material was used in the construction of the rod that was used in the attempt to pull the ball? If there is a hole through the obstruction, then the CO2 discharger or grease gun may not work. The touch hole liner will have to be removed to determine a thread pitch for zerk fitting for a grease gun. Because of potential interference issues, the touch hole liner should be removed before considering breech plug removal.
First remove the barrel from the stock. Soak the breech in a bath of penetrating oil. This may require a few days of soaking. If you have a touch hole liner, I would next go to the use of a high-pressure grease gun to move the obstacle. If there is a hole through the obstacle, then it is time to remove the breech plug.
"What about removing the breech plug? Is it even possible?"
I would try everything else before considering removing the breech plug. You will need the proper tools before attempting to removing the breech plug.
Yes, removing the breech plug is possible and is one of the possible means of removing the obstruction. Proper tools are required. Notably the tools include a heavy work bench, a very sturdy bench smooth jawed vise with wood and leather jaw liners to prevent marring and a very large breech plug wrench or large smooth jawed crescent wrench and a large hammer to provide some impact when trying to unscrew the breech plug. Once the breech plug is removed, a just under bore sized steel rod can be used to drive the blockage out through the breech.
There is so much unknown about the state of your rifle that we can go down about 15 pages of fanciful comments and still leave the obstruction in the barrel.
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