Plug fit with 54 cal barrel

[Nhgrants]

I bought a Colerain 54 cal round bottom rifled barrel that had the breech plug installed.
The breech plug is 5/8 inch diameter. I have read that the fit should be checked so when doing do I was surprised that there is very little shoulder for the face of the plug to bottom on. Should this barrel have have a larger plug installed ?

[rich pierce]

Opinions vary. There’s no doubt a wider shoulder is preferable but originals often had almost no discernible shoulder. I personally would not be bothered by a 5/8” plus in a .54.

[flehto]

Have you applied spotting compound on the plug face  to check if in fact there is a seal? Never experienced a lack of seal w/ a Colerain bbl but have heard comments on this. I've used Colerain bbls w/ the same plug/cal combo as yours, checked the seal and it was OK and had no further concerns......Fred

[smylee grouch]

Don Gets told me that the 5 8th plug was all he used in the 54s and had never had a problem

[rsells]

I have used the combo over the years with no problems.  I do prefer the 3/4 x 16 plug because it is easier for me to check the fit.
                                                                                           Roger Sells

[Dphariss]

Opinions vary. There’s no doubt a wider shoulder is preferable but originals often had almost no discernible shoulder. I personally would not be bothered by a 5/8” plus in a .54.

BUT. The originals were not built with modern manufacturing "tolerance" in the threads. The tap and screw plate were likely the same size without .003" of more "tolerance".  Something people routinely over look.  I don't trust installed breeches. Too To many horror storys. Like this one 5/8" 50 cal. The rebate on the plug actually was under bore diameter of the barrel.
I won't bother to mention the barrel maker's name. Just cause another sh@t storm. BUT ITS FAR TOO COMMON to have this sort of thing. Barrels tapped 2-3 threads deeper than the plug with a 54 with a 5/8" plug. I know of 3-4 reports.
I did pull a Rice barrel breech for a new guild member, I guess is something of an apprentice and the breeching was as perfect as could be. But its obvious some others just don't care. The bore scope photo of the cleaned plug back in the barrel shows the its possible to see past the rebate to the threads.
PULL THE BREECH. Chances are you will have to install a different plug or at least refit the existing plug. Sending it bad would be a waste of time. According to a friend who tried this. Don't want barrels with the breech installed. AND yes this barrel was not properly cleaned. But given the massive fouling trap it was impossible to get the fouling out at any rate.

Dan