According to Richard Townshend Bickers' excellent book, "The Battle of Britain", the Stuka began its dive from 15,000 ft./4,000 m. The dive angle was 80 degrees, and the maximum speed attained was 350 knts. The plane pulled out automatically at 4,000 ft. and the bomb was dropped.
MRPLUTO VMF-323 ~Death Rattlers~ MAG-33