Using adhesive tape on magazines is a common practice in many military and police units. Although it may seem improvised, it usually serves practical purposes. 

One of the most common functions is improving grip when manipulating the magazine during reloads. 

Tape can also help identify specific magazines within a unit’s equipment. 

Another possible use is reducing noise when magazines collide inside pouches. 
In some cases it is also used to mark magazines intended for specific ammunition. 

These small modifications show how operators adapt their equipment to real field needs.