Muskets

Flintlock muskets were the mainstay of most armies between 1660 and 1840. A musket was a muzzle-loading smoothbore long gun that was loaded with a round lead ball, but it could also be loaded with shot for hunting. Muskets had an effective range of about 75 to 100 meters. Smoothbore weapons that were designed for hunting birds called "fowlers". Flintlock muskets tended to be of large caliber rifle. Military flintlocks tended to weigh approximately ten pounds, as heavier weapons were found to be too cumbersome, and lighter weapons were not rugged or heavy enough to be used in hand to hand combat. They were usually designed to fit a bayonet. On modern weapons, bayonets are a last ditch weapon that rarely plays a significant role on the battlefield. On flintlocks, the bayonet played a much more significant role, often accounting for a third or more of all battlefield casualties. Flintlock weapons were not used like modern rifles. They tended to be fired in mass volleys, followed by bayonet charges in which the weapons were used much like the pikes that they replaced. Because they were used as pikes, military flintlocks tended to be approximately five or six feet in length, and used bayonets that were approximately 18 to 22 inches in length.
I think that flintlock muskets were the first major step for turning guns into what they are today. The musket was a very bulky and usually very inaccurate weapon. But it was a lot more efficient than shooting arrows at each other. Many battles were fought and won with the musket. Because of the inaccuracy of the weapon most of the killing was done by the bayonet rather than the lead ball that was fired from the gun. “This bayonet allowed well-disciplined infantry to withstand cavalry charges without the aid of specialized weapons such as the pike. For the next 150 years, infantry units armed solely with smoothbore firearms and bayonets were the backbone of all Western armies.”

Pike, John. "Rifle History." Military. GlobalSecurity.Org, 19/9/2007. Web. 13 May 2010. .