Comments by "" (@neutronalchemist3241) on "Terni M91 Carcano Semiauto Conversion" video.

We have a first hand account of the functioning of this rifle in Maj. Luigi Gucci book "Armi portatili" year 1915, p.58, and of the reasons it was not adopted. "The tested model, very simple, rugged, as handy as the M91, had shown a reliable, predictable and effective functioning, and it has a relatively low cost for the transformation. However, although the weapon could be assigned to some special troops, it's not convenient to adopt it for the entire army". The reasons were that the cost effectiveness was only apparent. In adopting a semiauto rifle for all the army, the price of the rifle was, in the end, marginal in respect to the price of the same cartridges for it (the price of a brand new semiauto rifle, not a conversion was estimated in 60L, that of a single Carcano cartridge was 0.1L, so a semiauto rifle costed like 600 cartridges), So it made little sense to adopt a solution that, "however ingenious, simple and well designed is, it's anyway a stopgap and, as such, it can't fully comply to all the requirements of an excellent infantry semiautomatic rifle."
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You are welcome, and thank you for the video. Knowing Gucci's book without having seen the rifle he was talking of, I was very curious about it. Seeing the rifle, it's easier to understand his reasons. IE, Gucci talks specifically of the barrel. The reason of the conversion is mainly to reuse the existing barrels (that are left untouched) as well as the receivers (that have to be remachined), the stocks (that have to be slightly reworked), and the magazine. At the cost of a new bolt, a recoil spring, and some minor parts. But Carcano barrels have been designed for a bolt-action rate of fire. Gucci, talking of a generic rifle's barrel of his time, says that it's internal reaches 450° after 80 rounds of rapid fire, and says that it has been estimated that the barrels of the converted rifles, due to the more rapid fire allowed by the semiauto operation, would have been worn out after about 2000 rounds. So there is little sense in using a less than optimal rifle to reuse a thing that is however destined to wear out quickly. We can make a similar consideration for the stock too. To save the receiver-barrel assembly, the shooter has the recoiling mass of the receiver directly ahead of his eye, and above his thumb. Although that's not really dangerous, it's surely discomfortable. the situation could be improved with a new stock, with the receiver a little farther from the shooter's eye and a more pronounced pistol grip that moves the thumb away from the receiver. But, that way, you don't save the existing stocks any more. Ecc... ecc...
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Superdude70 You are welcome!
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@robosoldier11 The analysis is of 1912. Then WWI happened (and semiautos like the Mondragon and the Remington Model 8) didn't impress there, unfit to trench warfare, they were relegated to the balloons of the artillery observers). However, this analysis, and the observations made during the war, led to the Terni 1921 prototype, already in an intermediate cartridge (7.35X32mm), that had been long evaluated. Then it was decided to not go with the intermediate cartridge and run a contest for a semiauto in 6.5X52 Carcano (the one won by the Scotti Model X). Then evaluations made on the Scotti in Etiopia, and the decision to switch to 7.35X51 cartridge anyway led to a new contest, that didn't end due to WWII.
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If you watch a video of the shooting of a Carcano, you can see that the aiming eye is way back, and the thumb had to be below the receiver already at the moment of shooting. However to have that recoiling mass close to the head, and to adapt the position of the trigger hand, is surely discomfortable, and is surely part of the reason the conversion wasn't adopted.
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It's not really a problem of reliability. It's that the cost of the conversion was not really that much lower than that of a new rifle to justify it's adoption instead of a brand new rifle.
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@robosoldier11 The Armaguerra 1939 had not been adopted, but approved for service. It means it could be distributed to the troops to test it on the field. As for not adopting anything, Italy is in company of practically everyone bar the US (the Soviets adopted one, but had to revert back).
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@robosoldier11 To me, as a technical enthusiast, both the Scotti action (the one you see in the Model X, it had been scaled up to 37mm automatic cannons) and the Breda gas action (the one you see in the Breda PG, that too had been scaled up to 37mm automatic cannons) were very good. The Scotti bolt was made of four pieces, with little precision machining required. The Breda of five, with only straight cuts. The Scotti rifle only required to fire from a closed bolt and a magazine to be a very good semiauto, and it's difficult to imagine a simpler one. But in 1939 Italy had 1/4 of the industrial output than Great Britain. There were budgetary constraints. France, that had other economic possibilities, adopted a new bolt action in 1936. In the same period, the US had something like 42% of the world's industrial output.
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The downsides were that it was anyway a stopgap. IE, for how much reliable and simple it could be, the entire receiver recoiling was uncomfortable for the shooter (you have the cheek and the thumb near to the recoiling mass) and the barrel was not apt for semiauto shooting (the higher rate of fire of a semiauto requires a shorter and thicker barrel to avoid overheat witout gaining too much weight). In the end, the saving was not enough to justify the adoption of a stopgap weapon.
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@robosoldier11 I would rather see those ideas used in new firearms. Like a Scotti action GPMG, or a Breda action AR. We've already seen good ideas given justice after decades of oblivion. The Steyr rotating barrel in the Beretta Series 8000 and PX4, the Bergmann floating lock in the Archon, the Revelli rotating lock (that of the Glisenti 1910 pistol and FIAT-Revelli 1914 MG) in all the 5.7x28 pistols bar the new S&W...
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Considering that the starting rifle was fairly light, probably not that much.
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