The Springfield was the USA's official service rifle during WW1.  It became the USA's official service rifle on June 19, 1903.  It was replaced by the faster firing M1 Garand in 1936.  It was a Bolt Action Rifle but they never used a sniper scope until it got replaced for being the service rifle.  It was in service as a Sniper Rifle from 1937-1957.  It was the main sniper rifle used in the Vietnam War and the Korean War.  Before the Springfield the USA was struggling when trying to design a  useful bolt-action rifle.  The Springfield was easiest to carry around and it had the best rate of fire out of all their bolt-action rifles.

The Mosin Nagant is a Bolt-Action Rifle used by the Soviet Union.  It had an internal magazine feeder which means whoever is shooting it doesn't have to pull back the lever to shoot again.  It was designed by Sergei Ivanovich Mosin and Belgian Emile Nagant, hense the Mosin Nagant.  It was used but in many different forms from 1891- to present day.  It was replaced with the SVD Dragunov as the Soviet Union's primary sniper rifle. 

The Soviet Union's main Sniper Rifle was the Mosin Nagant but they also had the PTRS-41 which was a more advanced sniper rifle and it was very effective against tanks and other heavy armored vehicles.  The PTRS-41 was the inspiration to different high powered sniper rifles such as the Barrett 50 Caliber.  The PTRS-41 was designed before WW1 but wasn't built until late in WW1. 

The M40A3 is the standard issue sniper rifle used by the US Marine Corps.  It has four variants, the M40, M40A1, M40A3, and the M40A5.  The M40's are made from the Remington 700 or R700.  The M40A3 is the sniper being used today but the M40A5 is being made and modified as we speak to be used by the US Marine Corps.  The original version of the M40A3 was an R700.  The M40A3 was introduced in 1996 but the M40 was made before that.  Some of the wars it has been used in are the Iraq War, Afghanistan, the Gulf War, Invasion of Grenada, Multinational Force in Lebanon, and the Vietnam War. 

The Barrett M82 was used by the United States as an anti-tank rifle.  The Barrett M82 is used as a Sniper Rifle but it also has metal piercing bullets.  This gun is used for taking down the outer shell on tanks so it becomes vulnerable for grenades and rocket launchers.  It recieved the nickname "Light Fifty" because it has a 50 Caliber BMG.  The Barrett M82 has 2 variants.  It was designed in 1982.  It has been in production since 1989 to present day.  The production of the other 2 variants have been stopped in order to make more of the Barrett M82 and because the other 2 were having different problems which made them not worth the time and money to make.