From Wikipedia, the free encyclopedia:
“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 Carcano 1891 rifle and many of its successors. In US
parlance, "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.
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 Maj. Antonio Benedetti, of the Brescia Arsenal, Secretary of the Commission and strong supporter of the advantages of smallbore cartridges, the 6.5x52 cartridge was definitively adopted in March 1890, prior to the rifle that had to use it (it would be the M91 Carcano rifle).
Since the adoption of the cartridge, the arsenals technicians worries 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 (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 6.5x52mm 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 2,000 metres. It was the first to be officially adopted of a class of smallbore military rifle cartridges such as the 6.5x50 Arisaka (Japan), 6.5x53R Mannlicher (Romania / Netherlands), 6.5x54 Mannlicher (Greece), 6.5x55 Swedish Mauser (also Norwegian Krag-Jörgensen), 6.5x58 Portuguese, of similar ballistic performances.
A comparison with other cartridges of the 7.62mm and 8mm calibre 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, and lacking of stopping power, compared to other military cartridges and rifles of the time. On the other hand, they seem to have a long list of advantages, as the flatness of trajectory, outstanding penetration at distance, less weight, less recoil, smaller dimensions, less material required to produce them.
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 barrel design, developed by the Brescia Arsenal at the same time of the cartridge, and first than the M91 Carcano Rifle, 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."
6.5x52mm Mannlicher-Carcano. (2009. March 7). In Wikipedia, The Free Encyclopedia. Retrieved 23:15, March 17. 2009. from http://en.wikipedia.org/w/index.php?title=6.5x52mm_Mannlicher-Carcano&oldid=275586983