Dave, What you describe is a common problem but a necessary one.
When I teach bezel making I always stress that it is better to make
the bezel a bit small rather than too large. When too large, it must
be cut and resoldered. Unless one has had a lot of practice, this can
result in even more problems including a burned bezel!
I don’t know what sort of bezel you are making. Is it with gallary
wire (these require stretching with a ring sizer otherwise the design
will be marred), does the bezel have a bearing attached (this will
often lead to unequal stretching) or is it a flat bezel (in which
case you simply have to be a bit more careful when hammering it).
ANNEAL THE PIECE. Even though you have just soldered it, it could
well not be equally soft through and through. Then just tap it up on
some round steel stock…sometimes it will be the end of a file or a
pliers handle, sometimes it will be a mandrel – depends on the size
and shape. Tap it only on one side – hang the stock or mandrel over
an open space so you are not tapping the top while flattening the
bottom. Tap very lightly three or four times while turning it and
switch sides, do the same and turn it again. Do this two or three
times until it fits snugly. Slight bottom distortion can be removed
by sanding it on a piece of 400 grit layed flat on a bench block.
Hope that helps. Cheers from Don at The Charles Belle Studio in SOFL
where simple elegance IS fine jewelry! @coralnut1.