I faced a problem of items - Claymore \ C4 \ AVmine are still exist in player's inventory, even if ammo is depleted. How and where can I make a condition, which checks and removes the item, if it has no ammo?

That is one weird question.
If u haven´t got any clays left, then there can´t be any left in inventory.

Plus, C4/Clay/AV Mine are all ammo/weapon combos. Carry 3 mines, place 3, then they should all be gone.

Otherwise probably change code.

DoS

I already found an answer. But you are wrong. Claymore that you carry in your hand, and the one that you place on the ground, they are not the same. In standard DLL, Claymore weapon is still remaining in inventory, even after ClaymoreExplosive ammo is depleted. Inventory system shows each weapon as it is, so it's important and necessary to remove the Claymore\AVMine\C4 weapons, when they have no ammo.
I solved Claymore\AVMine.

But C4 is a real problem. If I remove it after last projectile fired (I mean, last C4Explosive planted), the detonator won't work properly. It will just not explode planted explosives. And I don't even know, how to fix that.

Oh, thanks for telling me. I hadn´t expected that one still has stuff in inv after placing it.

Concernig C4: Hm....thats definitely tricky.You could try a delayed removal, but that wouldn´t help.I´m not sure whether u can do anything about that.

DoS