About this firing I mean close range up to 50-100 meters, especially when killing zombie with firearm.

Yes got same problem. I had plate carrier with attached pouches to it, and found gun holster, after attaching holster items from plate carrier disappeared. I lost: PSO-1, water bottle, AK-74 magazine and some food.

I must admit you should take a look on this problem, mayby it's optimalization? I have Windows 7 64 bit, i5 3570k, GTX 570 (overclocked 795 MHz core, 2150 MHz memory, 1590 MHz shader clock), 8 Gb CL-9 Kingston RAM, all setting, set to lowest possible, and card memory usage auto, even tried 1024x768 resolution and in towns, and cities I am geting FPS drop quite noticable. Dunno how much FPS is it but it seems like 20-25 in cities such Cherno or Elektro and about 30 in towns for eg. Vybor. Oh and especially FPS drop is in Zelenogorsk, this city is acutally unplayable when looking into city centre.