Pressure curve for a 203/96 gun. Massa proietto (shell mass: 102 Kg), Massa carica (charge mass: 100 Kg (NAC idk what it means)). Velocita’ iniziale (initial velocity (muzzle?) 1350 m/s), pressione max manometrica (maximum manometric pressure): 4070 Kg/cm^2
An interesting gun similar to the Paris gun or the USN's 9"/98 weapon.
Ah, yes. This is derived from the earlier 210/120, also an Ansaldo process based on reboring a 381/40.
Stefano Sappino had written about it on his blog, mostly pulling from an article in Storia Militare 01/2013 (Il “cannonissimo” Ansaldo by , Filippo Cappellano) and some archival material.
It spun out of a project to defend the Gulf of Genoa with heavy naval guns, which Mussolini then directed into a project to provide a railway gun that could bombard Malta from Cape Passero (which, to the grand harbor of Valetta, is a distance of about 100 km). This was intended to induce the British Mediterranean Fleet to abandon Malta as a major naval base... which they ultimately did anyways due to the air threat, relocating to Alexandria. Which rendered the gun project somewhat moot.
The 210/120 was supposed to fire a 115 kg shell at 1,500 m/s, achieving a range of 95 km at +50° elevation and 110 km at +55°. Though apparently dispersion was to measured 6 km (longitudinal) by 5 km (transverse) at 90 km...
The railway gun system came in at 300 tons and was tested in the late summer of 1930 with good results, and at least two guns seem to have been produced as in 1939 Ansaldo converted two of them into the above 203/96. Nothing is mentioned of what happened to these guns after this, however.
WRT to the above data for the 203/96 @Tzoli , N.A.C. is one of the solventless propellants introduced into service with the RM in 1936. It's full name was "Nitro-Acetil-Cellulosa", and was produced by Dinamite Nobel. The actual mix was 27% Nitroglycerine, 66% Nitro-Acetyl-Cellulose (Nitrocellulose with Ethyl Acetate as a solvent), and 7% Centralite. So in this case we are talking about a 100 kg N.A.C. charge.
The other type of solventless propellant introduced into the RM at this point in time was F.C.4 by Bimomprini-Parodi-Delfini, which used a mix of 8% Nitroglycerine, 65% Nitrocellulose, 4% Phthalide, 2% Centralite, and 1% Vaseline.
Either of these mixes (alongside the older Powder C) could also have KCl (Postassium Chloride) additives to create flashless powder, which before the start of WWII was extended to guns up to 152mm, and in 1941, 203mm (in fact Fiume had embarked the first load of flashless charges for 203mm guns and engaged in trials shortly before her loss at Cape Matapan). To my knowledge, no flashless powder was ever fielded for the battleship guns (320/44 and 381/50).
In is interesting to note that the KCl additive's specific effect was to turn the bright flashes into much duller violet pulses, which I have to imagine must have looked rather cool at night.
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