Complex sentence: With business booming, Colt entered an aggressive and expansionary phase and by 1855, Colt opened what was the world's largest private armament factory, the Colt Armory, in which he employed advanced manufacturing techniques such as interchangeable parts and an organized production line.
Split into simpler sentences: With business booming by 1855, Colt entered an aggressive expansionary phase and opened the Colt Armory, the world's largest private armament factory. He employed advanced manufacturing techniques such as interchangeable parts and an organized production line.