6 . 5×52mm Mannlicher - Carcano 6 . 5×52mm Carcano or 6 . 5×52mm Paraviccini - Carcano is an Italian military 6 . 5 mm ( . 268 cal , actually 0 . 2675 inches ) rimless bottle - necked rifle cartridge , developed from 1889 to 1891 and used in the Carcano 1891 rifle and many of its successors . A common synonym in American gun literature is " 6 . 5mm Italian " . In American parlance , " Carcano " is frequently added to better distinguish it from the rimmed hunting cartridge 6 . 5×52mmR ( U . S . version : . 25 - 35 Winchester ) . Ballistically , its performance is very similar to that of the 6 . 5×54mm Mannlicher - Schönauer . Design . Under the direction of the " Commissione delle Armi Portatili " ( Commission for Portable Weapons ) , instituted in 1888 to develop a smokeless - powder rifle for the Italian Army , the " Reale Laboratorio Pirotecnico di Bologna " ( Royal Pyrotechnical Laboratory of Bologna ) developed and tried several different cartridge designs , with a bullet diameter from 8 mm to 6 mm . Finally , due also to the influence of Major Antonio Benedetti , of the Brescia Arsenal , Secretary of the Commission and strong supporter of the advantages of smallbore cartridges , the 6 . 5×52 cartridge was adopted in March 1890 , prior to the adoption of the rifle that used it ( the Model 1891 Carcano rifle ) . After the adoption of the cartridge , the arsenals technicians worried about the characteristics of the original ballistite load , since that propellant was considered too erosive ( flame temperature of 3000 - 3500 °C ) and not stable under severe climatic conditions . Several other loads were tested , including the British cordite but without good results , until the " Reale Polverificio del Liri " ( Royal Explosives Factory of Liri ) developed a new propellant called " Solenite " , composed of trinitrocellulose ( 40 % ) , dinitrocellulose ( 21 % ) , nitroglycerine ( 36 % ) , mineral oil ( 3 % ) , and shaped in large tube - like grains . The new propellant , that reduced the flame temperature to 2600 °C and proved to be very stable , was adopted in 1896 and never changed until the end of the military production of the cartridge . The 6 . 5×52mm Carcano was designed as a full - blown infantry cartridge . In accordance with the tactics of the time , the adjustable rear sight of the rifle allowing for volley fire up to 2 , 000 metres . The 6 . 5×52mm Carcano was the first to be officially adopted of a class of similar smallbore military rifle cartridges which included the 6 . 5×50mm Arisaka ( Japan ) , 6 . 5×53R Mannlicher ( Romania / Netherlands ) , 6 . 5×54mm Mannlicher - Schönauer ( Greece ) , 6 . 5×55mm Swedish Mauser ( also Norwegian Krag - Jørgensen ) , 6 . 5×58 Portuguese . A comparison with larger bore smokeless powder cartridges of the 7 . 62mm and 8mm calibre class ( which class started in 1886 with the French 8×50mmR Lebel , continuing with the German 7 . 92×57mm , the Austrian 8×50mmR , the . 303 British , the Russian 7 . 62×54mmR , the Belgian and 7 . 65×53mm Argentine , the . 30 - 40 Krag , and the much later . 30 - 03 and . 30 - 06 Springfield ) may make the 6 . 5mm rounds appear " underpowered " on paper though , and lacking in stopping power . On the other hand , the small bore cartridges seem to have a long list of advantages , as flatness of trajectory , outstanding penetration at distance , less weight , less recoil , smaller dimensions , and less material required in production . Its short - lived intended successor cartridge , the 7 . 35×51mm Carcano , was intended to replace the 6 . 5 Carcano , but those plans were cancelled due to the logistics difficulties that arose once WWII commenced . The original 6 . 5×52mm barrel design , developed by the Brescia Arsenal at the same time as the cartridge before development of the M91 Carcano Rifle itself , used a gain twist barrel with deep rifling to reduce wear , extend barrel life and give consistent accuracy . Gain twist has a slow initial twist in the barrel progressively getting faster until the final twist rate is attained near the muzzle , resulting in less torque being imparted to the bullet during the highest stress phase of the interior ballistic cycle , and thus less barrel wear in the throat of the barrel . ( Gain twist was phased out in the last production of the Carcano rifle in favour of conventional rifling . ) Performance . With properly - bulleted ammunition , the 6 . 5×52mm Carcano is an effective deer cartridge up to about 200m ( 220 yards ) . Its main drawback in military use was that the standard Italian service round used a round - nosed , highly stable bullet that usually didn ' t tumble unless it hit bone , causing many narrow - channel , straight - through wounds . This characteristic is due to its high " sectional density " ( the ratio of a projectile ' s weight to its diameter ) . Hand loaders should note that the currently available factory ammunition may lack accuracy due to use of a 6 . 7mm ( . 264 in ) bullet instead of the 6 . 8mm ( . 268 in ) as originally loaded . Notable uses . The cartridge has achieved some notoriety , as a World War II Italian Carcano rifle was identified by the Warren Commission as the weapon used by former Marine Lee Harvey Oswald in his assassination of President John F . Kennedy .