Awesome question. Most of the weapons in the First World War where bolt action, and or spring operated. Most were a combination of wood and metal, and hard to clean and keep clean, which meant they were susceptible to stoppages.
Todays weapons have improved working parts and cycle of operations, as well as being gas operated and air cooled, leading to little to no stoppages on a well maintained weapon. Magazine sizes are bigger meaning that the weapon can fire more rounds before there is an ammunition stoppage. The weight of the weaponry is slightly less, but due to the ability to fire more rounds, the weight of ammunition has increased meaning that a soldiers pack weight has increased.
There are weapons being used today in service that were used in World War 1, one such weapon being the 50 Calibre Browning Heavy Barrel Machine Gun, due to its hard hitting fire power and calibre size, this Heavy Machine gun has been hard to replace with any other machine gun of its type.
Just realised you wanted pre WW1 weapons not Post. The weapons before the First World War were mostly single shot, barrel loaded weapons, or muscats. Machine guns were few, but one machine gun was the Vickers gun, which was very effective, but once again susceptible to stoppages due to the rounds being fed through the side linked with a hesion material.
Explosives where incorporated at the individual level as grenades WW1, whereas cannons where more likely pre WW1.
I hope this helps.
