[Lajko1]

Put me on right track, I'm thinking and can't figure out how is it possible to create anti ammo hack, not infinite one (that's comparing ammo stuff so far i know) but like anti spawn ammo, if you have gun and then you spawn like 50 ammo, how can I counter that?

[Kaperstone]

By keeping track of the weapons you give him.
When he switches a weapon OnPlayerUpdate is triggered, then you can check whether you gave him that weapon before or not.

Is a one way to protect against weapon spawning.

You can check how other anti cheats are doing it.

EDIT: https://sampwiki.blast.hk/wiki/OnPlayerWeaponShot you can play with it to track ammo (if you have lagcomp on)