[quote=“XPH2USN”]I have to agree with Jack, but from a different perspective. I have always been told that the Carcano is a weak action, but since they are or were cheap, I have ended up with half a dozen of them. I took a machine shop class at the local community college and tried to convert one of my pre-butchered Carcanos to 7.62x39. I never got the job finished, but in examining the bolt head, I noticed that the bearing surface of one of the locking lugs was rusty and the other lug looked polished. Obviously one bolt lug was doing all of the work. I showed it to my instructor, and he explained that parts that could possibly be subject to a life threatening failure are usually engineered for at least four, and more likely eight times the calculated strength requirement.
I went home and checked my other Carcanos. Only one, from 1918, had anything that resembled even minimal engagement of both lugs, with one lug fully polished and about half the bearing surface polished at the leading edge of the lug. The others were either rusted over or appeared to show tool marks (as apposed to scratches). I have shot all of these guns without problems. I have read that PO Ackley tested Carcanos to failure and did not agree with the “weak” assessment of other authorities. Perhaps the low pressures of Carcano ammunition reflect the known realities of Italian rifle manufacturing or perhaps the Italians were beginning to understand the drawbacks of overpowered rifle cartridges for less than well trained infantrymen.[/quote]
[quote=“JPeelen”]If you look at the rifle (fixed rearsight) and the bullet (not a spitzer but halfway between spitzer and round-nose) I think it was the Italians intention to equip the soldier with a low-recoil cartridge that is sufficient for the relatively short ranges expected in war.
Any weakness of the LMG cannot be the reason, because it also fired the more powerful 6.5 mm. The propellant was in my view chosen to have no big void in the case.[/quote]
[quote=“Fede”]According to the Italian publication dated 1938: “The determinant reason of the transformation is to be found in the evolution of tactical criteria, procedures for action and mode of use of infantry firearms, which now exclude the opportunity of shooting with a rifle beyond those distance limits that do not allow the accuracy of aiming”.
The new cartridge and rifle were made according to the following requirements: 1) Ballistic improvement over the 6.5 mm up to the distance of 4.500 m; 2) Lighter cartridge and lighter bullet; 3) Caliber between 7.5 and 8 mm [in practice, the 7.35 mm caliber was chosen because it was the maximum allowed in a worn-off barrel of 6.5 mm caliber]; 4) Keep the characteristics of M. 91 in use as much as possible (streght, rusticity, simplicity, easy assembly/dissasembly, etc.); 5) Minimal need of modification work; 6) Ensure the operation of the cartridge in the Breda M. 30 machine gun using a new barrel and without altering the mechanical quality.[/quote]
The assessment that the Italians wanted what we would now call an “intermediate” cartridge is supported by the information contained in this thread.
[quote=“TonyWilliams”]I have been told by an Italian with an interest in arms history that the reason for the development of the 7.35mm, rather than just designing a spitzer bullet for the 6.5mm (as the Japanese did) is that a large proportion of the 6.5mm Carcano barrels were shot out, with no rifling left. The Italians couldn’t afford new barrels (they were chronically short of cash) so they simply bored out the existing barrels to the larger calibre, cutting new rifling as they did so.
This would likely account for using such a low pressure, since the barrel would be thinner.[/quote]
That doesn’t sound likely; as experiments Hatcher did shaving down M1903 barrels to extreme thinness showed that even with high pressure calibers, barrels are much heavier than they need to be from a structural perspective. Unless the Italians had far inferior metallurgy (unlikely, IMO) to the Americans, the explanation that most makes sense to me is that the Italians wanted an intermediate cartridge, and the propellant that they could make in quantity required a case that large to house it. The low peak pressure produced was most likely a byproduct of this arrangement. The same effect can be seen in .303 British; the powder fills the case completely despite the relatively low peak pressure.
Thanks for everyone’s help with this. It seems the Italians can be credited with fielding the first (purpose-designed) intermediate caliber, after all.