Complex sentence: At the age of 13 he went to sea, and in 1897, at the age of 16, he hunted lions for the Uganda Railway using a single-shot rifle chambered in.303 British.
Split into simpler sentences: At the age of 13 he went to sea. In 1897 at the age of 16 he hunted lions for the Uganda Railway using a single-shot rifle chambered in.303 British.