There are some here who are more knowledgeable
about pressures in firearms than anyone else I've
found on any other 'net forum, so I pose these
questions to you in hopes of settling a debate.

The photos below are that of a Savage type
muzzleloader breech plug. Even after having been
wiped off with a rag, one can tell that there has
been carbon blasted rearward past the two
forward threads:



Carbon is also very evident behind the shoulder
of the breech plug snout:



Prior to partial cleaning, the whole snout area
between the front of the breech plug to the
threads was blackened with carbon.

The shoulder was supposedly designed to seal
gases from travelling rearward, but this is
clearly not the case. This brings up my
question. Is there enough restriction to keep
pressures behind this shoulder much lower than
barrel pressures until the bullet exits the
barrel?

The mating surface on the breech plug shoulder
and the shoulder in the barrel is actually
only about 1/3 of the circumference of the
shoulders. Carbon forced gas has blackened
the other 2/3's. This instance is not just
confined to this plug. It has been the same
story with four different plugs in two
different barrels. So, does anyone have any
educated guesses/ideas what per cent of
pressure the barrel in the area around the
breech plug snout is getting in comparison to
the business end of ignition in the barrel?