It has happen to the best of us. We spent hours pouring all of our love into and upon removal of ring from kiln its too small. Even worse it was sent to customer and it is wrong size. Well there is a solution in most cases to adjust 1/2 to 1 full ring size. This technique will work for resizing, re-rounding, and sometimes correcting un-even shrinkage.All you need is a metal mandrel, something hard to tap against and physics does the rest.
The following video demonstrates a easy technique to re-size or re-round a metal clay or silver pmc ring.
Please take note as this video demonstration assumes the following
1.The ring must have a strong seam.
2.It only works within 1/2 to 1 ring size.
3.Better to repeat the technique many times over gently to achieve size then to try to accomplish in one pass such as in video.
4. For wide(and even not wide) band rings always repeat technique equally on both sides of ring.
5.This will only enlarge a ring that is too small.
6.Use only your hand or a rag inside your hand to hold ring. This prevents marring of outside and helps soften the impact and shock to ring.

Best wishes,
Margaret
David