Hi, Hammy and Chad,
The Nagant revolver round could be called the 7.62 x 39R, although I have never seen it referred to that way. It is not the same as the 7.62 x 39 rifle cartridge for the SKS and AK. The cartridge case of the 7.62 Nagant is so long because it contains the bullet and has enough extra length to insert the case mouth into the end of the barrel, thus sealing the barrel-cylinder gap.
The .32 ACP cylinders, needless to say, do not provide this sealing.
Chad,
The .32 ACP does not need a moon clip in those new cylinders because it is semi-rimmed. A clip would not aid extraction, since the Nagant is a solid frame with a rod ejector.
Jim