Complex sentence: The counter-battery proved accurate, with several of the 16 inch shells finding their mark, one igniting a huge explosion as the ammunition storage for one of the guns went up in a massive fireball.
Split into simpler sentences: The counter-battery proved accurate, with several of the 16 inch shells finding their mark. One shell penetrated the ammunition storage for one of the guns, igniting a huge explosion as the ordinance went up in a massive fireball.