Hugh-
I assume (assumption being the master of all %^&*-ups) that this is a flintlock barrel, or, rather, one that is destined to become a flintlock.
If it's not, please disregard this and all previous posts. If, however, your barrel will eventually have a touch hole (as opposed to a snail percussion thingy) there are a number of perfectly legitimate reasons why you would want to have the breech plug out of your tube. (If, for instance, you want to lap the rifleing, or slug the barrel.)
I was greatly frustrated once by the same problem, and had to return a barrel which had had a plug installed 'at the factory' in order to have the breech plug removed without damaging/ruining the whole deal. This can be especially troublesome if you're putting the barrel into a preinlet stock, so if it's messed up at the breech, rethreading isn't an option because the swamping will no longer fit the stock if the barrel length has been changed. Luckily for me, I had reversed my rectocranial inversion before it came to that.
A short while later, a thread appeared on this very site, which described in lurid detail the process by which one removes the breech plug. I can't seem to get the thread number of the discussion, but if you bang away with the forum's internal search engine, it should eventually reveal itself. The process, by the way, involves a good bit of clamping in hyge vises and the application of LOTS of leverage. (Someone mentioned a three foot cheater bar or somesuch- sounded like it was way out of torque spec when it got here, so I wasn't gonna fool with it.)
The short version of this tirade is that you will probably find it safer and cost effective to send the barrel out to a 'smith (I used Track, where i bught my breeched barrel in the first place). They will charge you for the service, but you'll get the barrel back in one piece (along with the plug) and things won't be all torn up.
good luck with your project!
msw
