at the muzzle of the rifle, which over time developed into a tube with a circular ring aperture so that the black 'bull' would be viewed within the foresight ring which in turn was centred in the rear aperture. This arrangement improved the accuracy as the sight distance was increased with the aperture sight closer to the marksman than that of the military 'iron' rear leaf sight fitted directly to the barrel. Calibers Fullbore Target Rifle involves prone position single shot precision shooting using adjustable aperture sights at 'round bull' targets at distances from 300 to 1000 yards, with each shot being carefully scored and analysed. The usual calibre used was .303 British (standard military) up to the late 1950s when the NATO countries adopted the .308 Winchester/7.62×51mm NATO as the new military interoperable choice of ammunition. Under ICFRA Rules, .223 Remington/5.56x45 NATO is permitted as an alternative. However, many matches such as the NRA Imperial Meeting require competitors to use issued ammunition - which is typically only offered in .308. The .303 British calibre is still in use by Service Rifle shooters and was exclusively used by Fullbore in the Short, Magazine Lee–Enfield (SMLE) No.1 Mk. III and Lee-Enfield No. 4 rifles. Clothing Modern target rifle shooters commonly use specialised stiff leather or canvas shooting jackets to maintain a stable prone position. Riflemen also widely wear shooting gloves on their support hand to stabilise the rifle and to protect the hand from a single point sling. Competitions World Championships have been organised by ICFRA since 2003 and are held on a four-year cycle. Championships for TR-Class and F-Class are held separately, offset by two years. The TR Championship includes both an individual and a team event. The Team event is known historically as the Palma Match and the Team World Champions are awarded the Palma Trophy, which dates to 1876. Fullbore Rifle is contested within the Shooting events at the Commonwealth Games. These are the only major multi-sport Games to include the discipline, with other events such as the Olympic or Asian Games focussing on ISSF-regulated smallbore and air rifle disciplines. The Commonwealth Shooting Federation also holds a CSF Championship in the run-up to the Games, serving as a test-event for the Games venues and final selection opportunity for Games squads. The Imperial Meeting, organised by the British NRA at the National Shooting Centre, Bisley is regarded as one