I too agree to try and shoot it out, not that I like that idea so well, but once you move a breech plug you will never get it tight and also alined again.
If the gun is a hexagon you will never really match the points again and then if it is a round barrel still the sites will end up off center, in both cases...
The tangs will be off but won't line up anyother way byt down and screw to true, which will put everything else out of wack.
To not tighten the breech fully will mean gasses could escape and or gases will crud up the threads as the seat won't fit.
A breech plug has a taper to fit up on tight in the bore wider than the threads something like a valve in a internal combustion engine has, A seat and a valve face to seal hot gasses..
It is not common to pull breech plugs.