The press ( screw or “fly” press, to be exact) is a run-of-the-mill Blacksmiths and metal workshop bench tool for doing small jobs ( punching holes, riveting, making ( cutting) small caps, etc) when equipped with an array of tool dies, swages, etc.
I have a larger ( 5 ton model) in my workshop and I use it for “re-drawing” cartridge cases and swaging lead Bullets.
The process, as described by another Poster is simple. “Push in-Push Out” dies are used for reforming the cases; (once dismantled); the Projectiles are “down-sized” by a simle “Push-thru” die ( as with resizing Lead Bullets to correct Groove diameter for reloading in [modern] shooting ).
There are also “straight-line” loading dies, to reseat the reformed Bullet in the (re-filled) reformed case. All very simple, notably slow, but effective… May be a Hundred rounds every couple of hours ( between disassembly, sizing, re-assembly.)
As to extractability of the Reformed rimless cases, the extractor on a Mosin-Nagant is beefy enough to engage the groove and rim of a 7,9mm case ( even though it is some 10-15 thou smaller than a 7,62x54R case, (head) or 50-60 thou rim difference. I suppose occasionally the rod would have to be resorted to to clear an unextracted case…
With the 9x19 conversion to 7,62x25, another problem arises…the 9mm case reaches only as far as the beginning of the shoulder of the 7,62x25…so it is the Bullet which is “Partially swaged” to form a “7,62” Nose, with a shouldered “skirt” still at 9mm, to seat in the case neck. Thus the complete round will “chamber” and “headspace”, and on firing, the “skirted” projectile will swage down fully to 7,62, and go down the barrel…a bit rough for a Blowback operated gun ( PPSh, PPS etc.) but Barely Functional. Could be a bit too much pressure for a locked breech Pistol ( Mauser C96 or Tokarev.)
Definitely only for lead cored Bullets, would not work with Sintered iron 9mm.
Extraction is not a problem, as the rim dimensions of both cartridges are roughly similar.
I would think this was a “make do” early war ( 1941-early 42) solution to Partizan ammo problems, but soon resolved by the Plethora of Ammo captured from the Germans ( even 7,62 as well). BY 1943, partizan groups were well supplied, and also in regular contact ( directly by runners and also radio contact with their masters on the Russian side of the front).
So much so, that by war’s end, many “Partizan” groups were rounded up by the NKVD, and on the charges of “consorting with the Enemy” and “fleeing the battlefield” ( originally in the Debacle of 1941), were packed off to the Gulag for between 8 to 20 years ( Section 58, “Anti-Soviet Activity”).
The Information supplied above is Purely Historical in nature, and Not meant to be Possible "Reloading " Info as per Forum Rules.