So, many older pistol designs used a barrel in a fixed position in relation to the pistols frame. Due to this configuration, the added weight of a suppressor hanging from the barrel does not impede the mechanical operation of the slide cycling.

Modern pistol designs utilize variations of John Brownings tilting barrel design. Because the barrel tilts during the cycling of the pistol, the weight of the suppressor interrupts the movement of the barrel and slide preventing a full stroke of the slide to eject the spent case and feed another round from the magazine. Not good.

In response, something called a Nielsen device was developed, basically a cylinder with a spring in it that encourages the pistol slide to fully cycle. These are sometimes referred to as a “piston” or “booster”.

Suppressors are heavily regulated by the ATF, and id have to guess that when seeking one on the grey or black market, or manufacturing your own, a Nielsen device is not easy to replicate with crude means, nor easy to find on the street.

TL:DR dude was missing a part that makes a pistol work more gooder with a suppressor.

Source: I gun.