From the start of the modern biathlon in 1958 until 1965, international competitions were held exclusively using high power centerfire cartridges (such as the .30-06 and 7.62 NATO). Fullbore biathlon was part of the Winter Olympic Games in 1960, 1964, 1968, 1972 and 1976. Fullbore World Championships were held from Saalfelden 1958 to Vingrom 1977, with Lake Placid 1973 being the first time the World Championships took place outside Europe. Caliber discussions was a recurring subject, and there was a long trend of different nations moving towards various 6.5 mm or smaller calibers. In 1976 it was decided by the International Modern Pentathlon Union (UIPM) that all international championships starting from 1 January 1978 would be conducted using the .22 Long Rifle (LR) smallbore caliber. The last major championship using fullbore rifles was the 1977 World Championship in Vingrom, Norway. From 1978, .22 LR smallbore was the official caliber in international biathlon. High power centerfire cartridges are, however, still used today in Nordic field biathlon and moose biathlon competitions. In 1960, the sole event was the men's 20 km individual, with shooting at the four distances of 100, 150, 200 and 250 meters. From 1963, all biathletes switched to cartridges based on the 6.5 mm projectile. As a result, the Soviet Union developed the Bi-6.5 rifle and the new cartridge .220 Russian (5.6×39mm) (which would later lead to development of the famous 5.45×39mm military cartridge). The newly developed 5.6×39mm cartridge was also used in 100 meter running deer competitions in specially developed sport rifles such as the MBO-1M and MBO-2 () straight pull rifles, as well as the MBO-3 pump rifle. In 1966, with the addition of the relay event, the target distance was reduced to 150 m. The shooting range was reduced to 50 m in 1978 with the standardization of the rimfire cartridge, and the self-indicating targets used today made their debut at the 1980 Winter Olympics. While international biathlon switched to smallbore, Nordic field biathlon and moose biathlon continued to use fullbore rifles. Currently only iron sights are permitted in field biathlon, and the firearm must be on an approved list. In moose biathlon however, any scope and fullbore rifle legal for moose hunting are permitted, and the ammunition also has to satisfy the legal kinetic energy requirement for hunting moose.