FWIW, on the rate of fire of the 65mm/64, some background may be useful.
The program was announced in November 1938 original tender (set to expire on 30 March 1939) went out to four companies - Ansaldo, OTO, Isotta Fraschini, and Breda.
The original requirements called for a 65mm/60 with the following characteristics;
Mass: 580 kg
MV: 850 m/s
RoF: 30 rpm
The first gun system was supposed to be ready in December 1939, and the rest (total of 78 to be built, for the Capitani Romani) were all to be completed and delivered by the end of 1941.
The winners, Ansaldo, worked with Terni and initially produced a 65/56, which then grew to an /62 and finally /64. One source I have actually gives the rate of fire as 25-30 rpm, and a lower MV and range of 850 m/s and 6,300 meters - this may reflect the earlier lower-caliber length versions, versus the usually reported 950 m/s with a range of ~7,500 meters? The rate of fire seems to reflect what Ansaldo intended to achieve with the electrically powered automatic fuse loader and power rammer system. Ansaldo-Terni only began serial production in 1942, with 60 delivered by March 1943 and a total of 73 by July 1943.
It is also interesting to note that some information exists on the two other prototypes submitted. Breda's effort was a 65mm/58, evaluated in December 1940 and November 1941, had an MV of 850 m/s and a maximum elevation of +70°. These prototypes were rejected, and unfortunately I have no more information on them. Caproni (via their subsidiary Isotta Fraschini) also developed a 65mm/58, which was a stabilized model. The prototype apparently was only completed in 1943, but featured impressive performance - a 4.3 kg projectile fired at 850 m/s to a maximum range of 11,750 m, and a rate of fire of 50 to 55 rpm. It was, however, relatively heavy, with the entire system coming in at 7.25 tonnes (metric).
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