[Padarom]

I would try to create a very frequent timer (or maybe OnPlayerUpdate) and a boolean like bool:ToldOutOfAmmo[MAX_PLAYERS];
Every time the timer passing you check wether or not the player has a weapon (just check his weapon-id) and then GetPlayerAmmo. If it's 0 check if ToldOutOfAmmo is true, else send a message to him and set it to true.
For the /reload just use SetPlayerAmmo then.
Hope it helped.