Complex sentence: Gunnison was built in 1903 as a twin six inch Disappearing gun battery and in 1942 the battery was altered to accept two M1900 six inch pedestal mounted guns along with the addition of two shell hoists and a plotting room.
Split into simpler sentences: Gunnison was built in 1903 as a twin six inch disappearing gun battery. In 1942 the battery was altered to accept two M1900 six inch pedestal mounted guns along with the addition of two shell hoists and a plotting room.