Gzh literally means gilza geleznaya (Gilza leeznaya) - iron sleeve. Most types of 9x18 mm ammunition (some I know, such as PMM and RGO28, but others alluded to me, it would also help me to know what gzh means). The best 9×19 ammo Tarkov has to offer, which is only available in the last game to players via a level 3 workbench. However, this is far from a cheap or fast method, so it's unlikely that you'll be able to accumulate enough ammunition stockpiles, especially given the rate of fire of the weapons you'll be using.
However, when you have an arsenal, this is your default option, as it offers the highest penetration value of all 9×19, making it capable of taking on well-armored opponents. To conserve your ammo, you'll want to use your secure container and minimize the total number of magazines you bring to the raid when using this round. Understanding the underlying mechanics of how ammunition works in Escape From Tarkov can provide additional insight into what makes a type of ammunition good or bad for those who want to go beyond reliance on an EFT ammo card resource. A 7.62x39 mm PS gzh (GAU index - 57-N-23) cartridge with a 7.9 gram bullet with a heat-strengthened steel core with lead coating on the tip and a bimetallic cover, in a bimetallic housing.
We recommend that you carry the TT with GZH shells as a high-penetration backup if you run out of ammo for your primary weapon. Those with little experience using real firearms already have a lot of obstacles to overcome in Escape from Tarkov, as most guns feature more than ten different components, so it's understandable to struggle to choose between the different types of ammunition sold between different vendors. EFT Monster is producing a high-quality Tarkov bullet visual graph that is also interactive and allows you to understand where each ammunition is located in terms of damage and penetrating power.
