6.5x52mm Carcano or 6.5x52mm Mannlicher-Carcano is an Italian military 6.77 mm (.266/67 cal.) rimless bottle-necked rifle cartridge, developed from 1889-1891 and used in the M 91 Carcanorifle and its successors. In US parlance, the moniker "Carcano" is frequently added to better distinguish it from the rimmed hunting cartridge 6.5x52mmR (US version: .25-35 Winchester). Ballistically, its performance is very similar to that of the 6.5x54mm Mannlicher-Schönauer.
Originally, the 6.5x52mm 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 2000 metres. Its ballistic performance is in the same class as other contemporary military rifle cartridges such as the 6.5x50 Arisaka (Japan), 6.5x53R Mannlicher (Romania / Netherlands), 6.5x54 Mannlicher-Schönauer (Greece), 6.5x55 Swedish Mauser (also Norwegian Krag-Jörgensen), 6.5x58 Portuguese.
A comparison with other cartridges of the 7.62mm and 8mm caliber class (starting in 1886 with the French 8x50R Lebel, continuing with the German 7.92x57, the Austrian 8x50R, the British .303, the Russian 7.62x54R, the Belgian and Argentine 7.65x53, the .30-40 Krag, and the much later .30-03 and .30-06) may make all these 6.5mm rounds appear "underpowered" on paper though, compared to other military cartridges and rifles of the time.
Its short-lived intended successor cartridge, the 7.35x51 Carcano, is sometimes identified as the first intermediate round, before the German 7.92x33 and the Soviet 7.62x39.
The original 6.5x52mm Carcano design 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 full twist rate is attained at 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.
The 6.5x52 Carcano is an effective and easy-to-shoot deer cartridge out to 200 yards, with properly-bulleted ammunition. Its main drawback in military use was that the standard Italian service round had a round-nosed bullet and was highly stable (did not usually tumble unless it hit bone), giving many narrow-channel straight-through wounds. This characteristic is due to the high sectional density of the round (the extreme bullet length compared to its diameter) and probably accounts for the "magic bullet" that managed to fatally wound John Kennedy and seriously wound Governor Connelly and was later found on a stretcher in Parkland Hospital.
Handloaders should note that the Carcano rifle action is not as strong as a Mauser-type or other modern bolt-action rifles, and should resist temptation to increase the 6.5x52mm Carcano performance. Though dimensionally similar, load data for other cartridges such as the 6.5x55 Swedish cannot be substituted. Currently available factory ammunition may lack accuracy due to use of a .264 bullet instead of the .268 as originally loaded.