Complex sentence: The first, "Baby Babylon", was a horizontally-mounted device which was simply a prototype for test purposes, with a bore of 350 mm (13.8 inches), and a barrel length of 46 metres (151 feet).
Split into simpler sentences: The first, "Baby Babylon", was a horizontally-mounted device which was simply a prototype for test purposes. It had a bore of 350 mm (13.8 inches), and a barrel length of 46 metres (151 feet).