the crossed rifle symbol has been the insignia of the infantry since the mid 1800s there were other symbols such as the hunting horn witch was common until the turn of the 19th century to the 20th century.
There were several innovations in the time period such as the Henry repeating rifle and the Sharps carbine and rifle. The first steps to the automatic weapon were also made in this era in the form of the Gatling gun. PICS OF THE GUNS BELOW IN THE ORDER MENTIONED