Here is a CZ 52 that was converted to 9mm from 7.62X25mm Tokarev. Down below is an excerpt from Wikipedia explaining how this pistol works.

The CZ 52 utilizes a fairly uncommon short recoil operating system in which two vertical rollers are used to lock the barrel and slide together, via a cam block.^[4] This is similar to the system used in the German MG 42 machine gun. This arrangement results in a strong lockup which, conventional wisdom holds, allows the loading of higher pressure ammunition (such as ammunition intended for use in a submachine gun) with higher velocity and energy than compatible ammunition manufactured for pistols of a similar caliber in other Warsaw Pact countries.^[6]

When cocked, loaded, and closed; the recoil spring, positioned coaxially around the barrel, provides the pressure necessary to lock the barrel and slide together via the rollers. When a round is discharged, the barrel and slide recoil together while the cam block is held stationary by a lug in the receiver. After traveling rearward a short distance (about 0.16" or 4 mm), the rollers are allowed to disengage from the slide via recesses in the cam block. At this point, the slide is free to continue rearward, cocking the hammer, extracting the spent case from the barrel's chamber, and ejecting it clear of the pistol. After reaching the end of its stroke, the slide is returned to cocked and loaded by the compressed recoil spring, again collecting a fresh cartridge from the magazine and inserting it into the chamber.^[6]

Last two pictures show when the barrel is locked and unlocked in the slide.