why would the outside of a case neck be burned after firing?
is this a bad sign? sloppy chamber or over crimping possibly?

possible light load which did not expand the neck enough to seal the chamber, allowing the hot gases to escape past the mouth of the case, burning the outside of the neck.

If you are talking about black carbon deposits it is normal to have part of the neck or sometimes the whole neck exhibit this as long as the soot doesn't go any further down think nothing of it.
bigbull

i'm using sierra's accuracy loads which do seem light compared to other manufacturer's specs, but, they do work exceptionally well. the case necks are all discolored with a dark ring right around the top of the shoulder angle.

Sometimes a slow powder will give a black neck.
Not to worry.
Good Luck!

and it CAN be a sign of low pressure... blackened necks mean the neck wasn't blown out to seal... can be a hassle.

jeffe