Question: The PU scope (ПУ, прицел укороченный, 'Scope short-cut' in comparison to PE scope) is a sniper scope of Soviet manufacture, widely used on the Mosin–Nagant and which Soviet semi-automatic battle rifle?

Context articles: FM57 rifle
PU scope
2012 College Station, Texas shooting
SKS
SLEM-1
Berdan rifle
Simo Häyhä
MAS-49 rifle
Type 99 sniper rifle
SVT-40

The FM1957 is a Swedish prototype battle rifle based on the Ljungman Ag m/42 semi-automatic rifle.
 Along with the FN FAL, M14 rifle, Rk 60 and GRAM 63 battle rifle, it was in competition to replace the bolt action Mausers and the Ag m/42 rifles in Swedish service during the early 1960s but lost over the Heckler & Koch G3 (license built as the Ak 4 in Sweden).
 The FM57 therefore never entered serial production.
 The rifle was built in two calibers: the 6.5×55mm (standard in the Swedish Armed Forces at the time) and the 7.62×51mm NATO (which later replaced the 6.5 mm cartridge in Swedish service).
The PU scope (ПУ, прицел укороченный, 'Scope short-cut' in comparison to PE scope) is a sniper scope of Soviet manufacture, widely used on the Mosin–Nagant and SVT-40.
 The scope was fixed at 3.5 power magnification.
 The reticle could be adjusted vertically for range, from 0 to 1300 meters.
 Horizontal adjustments for windage were also provided.
On August 13, 2012, a shooting occurred in College Station, Texas near Texas A&M University around 12:30 p.m. central time, in which multiple people, mostly police officers, were shot in a shootout.
 The suspect, who was shot and fatally wounded in the gunfight, was later identified as 35-year-old Thomas Alton Caffall III.
 Police found a Vz 58 Tactical Sporter rifle, a Mosin–Nagant M91/30 rifle with a bayonet, a .40-caliber SIG Sauer P226 pistol stolen from a police officer, and a PSL rifle with a scope in his house after the shooting.
The SKS is a Soviet semi-automatic carbine chambered for the 7.62×39mm round, designed in 1943 by Sergei Gavrilovich Simonov.
 Its complete designation, SKS-45, is an initialism for Samozaryadny Karabin sistemy Simonova, 1945 (Russian: Самозарядный карабин системы Симонова , 1945; Self-loading Carbine of (the) Simonov system, 1945).
 The SKS-45 was manufactured at Tula Arsenal from 1949-1958 and at Izhevsk Arsenal in just 1953 and 1954, resulting in a total Soviet production of about 2.7 million carbines.
 In the early 1950s, the Soviets took the SKS carbine out of front-line service and replaced it with the AK-47; however, the SKS remained in second-line service for decades.
 It is still used as a ceremonial firearm today.
 The SKS was widely exported, and was also licensed for production by then Eastern Bloc nations, Romania and East Germany, as well as China, where it was designated the "Type 56 Carbine".
 The East German version was known as the Karabiner S, the Albanian as the Model 561 and North Korean as the "Type 63".
 The SKS is popular on the civilian surplus market as a hunting and marksmanship semi-automatic rifle in many countries, including the United States, Canada, and New Zealand.
 Its age and numbers make it relatively inexpensive to purchase, and steel cased 7.62x39mm ammunition is one of the least expensive center fire cartridges currently on the market.
 The SKS was the second firearm to be chambered for the 7.62×39mm M43 round, with the first being the RPD.
The SLEM-1 (Self Loading Experimental Model 1) was a semi-automatic battle rifle.
 The weapon is gas-operated, semi-automatic and feeds from a 10-round magazine.
The Berdan rifle ("винтовка Бердана"/"vintovka Berdana" in Russian) is a Russian rifle created by famous American firearms expert and inventor Hiram Berdan in 1868.
 Standard issue in the Russian army from 1870 to 1891, the Berdan was replaced by the Mosin–Nagant rifle.
 Widely used in Russia as a hunting weapon, sporting variants, including shotguns, were produced until the mid-1930s.
Simo "Simuna" Häyhä (] ; 17 December 1905 – 1 April 2002), nicknamed ""White Death"" (Russian: Белая смерть , "Belaya Smert" ; Finnish: "valkoinen kuolema" ; Swedish: "den vita döden" ) by the Red Army , was a Finnish sniper.
 According to western sources, using a Finnish-produced M/28-30 rifle (a variant of the Mosin–Nagant rifle) and the Suomi KP/-31 submachine gun, he is reported as having killed 505 men during the 1939–40 Winter War, the highest recorded number of confirmed sniper kills in any major war.
 However, Antti Rantama (Häyhä's unit military chaplain), credited 259 confirmed sniper kills were made by Simo Häyhä during the Winter War.
 Häyhä wrote in his diary, found in 2017, that he killed over 500 Soviet soldiers (by both sniper rifle and machine/submachine gun).
The MAS-49 is a French semi-automatic rifle that replaced various bolt action rifles as the French service rifle that was produced from 1949.
 It was designed and manufactured by the government-owned MAS arms factory.
 The French Army formal designation of the MAS-49 is Fusil Semi-automatique de 7,5mm Modele 1949 ("semi-automatic rifle of 7.5mm model 1949").
 The MAS-49 semi-automatic rifle was produced in limited quantities (20,600 units), whereas the shorter and lighter variant, the MAS-49/56, was mass manufactured (275,240 units) and issued to all branches of the French military.
 Overall, the MAS-49 and 49/56 rifles gained the reputation of being accurate, reliable and easy to maintain in adverse environments.
 All the MAS-49 and 49/56 rifles feature a rail on the left side of their receivers to accommodate a designated rifle scope.
 The MAS-49 and MAS-49/56 were replaced as French service rifles by the FAMAS assault rifle in 1979.
The Type 99 sniper rifle (九九式狙撃銃 , Kyūkyū-shiki sogeki-jū ) was a Japanese sniper rifle used during the Second World War.
 It was a sniper version of the Type 99 rifle, chambered in the 7.7×58mm round.
 There were a few variations of the Type 99 sniper rifle, some with the straight bolt and the scope mounted on the left side of the receiver which allowed use of stripper clips.
 Another variation was one with a bent bolt and the scope above the receiver which required the sniper to load the rounds one at a time.
 The shorter barrel, combined with the larger caliber round made concealment more difficult than the Type 97 rifle that preceded it, considering the louder muzzle blast and flash caused by the increased powder capacity.
The SVT-40 (Samozaryadnaya Vintovka Tokareva, Obrazets 1940 goda, "Tokarev self-loading rifle, model of 1940", Russian: Самозарядная винтовка Токарева, образец 1940 года) is a Soviet semi-automatic battle rifle.
 The SVT-40 saw widespread service during and after World War II.
 Intended to be the new service rifle of the Soviet Red Army, production was disrupted by the German invasion in 1941 resulting in a change back to the older Mosin–Nagant bolt-action rifle for the duration of World War II.
 After the war new rifles were adopted by the Soviet Union, such as the SKS and the AK-47.