For really dark eggs I find day 14/15 is the sweet spot. Use a very dark room & an led light. Look for shadows of movement or the outline of blood vessels near the air cell. It worked for my Marans eggs this last hatch.
@wabbit1964 I am so sorry about your turkeys. I had a rough hatch last year with them too.
@wabbit1964 I am so sorry about your turkeys. I had a rough hatch last year with them too.