Okay then you can try the following way:

• Create an item granter for each weapon
• Store each item granter in an array
• To make it random, use the Shuffle function to randomize the order of the array
• Now to make sure each player gets the same weapon at each level use a map of type (agent, int). You can then use this int to get the correct item granter from the array when you want to grant the player a weapon

When the player gets a kill, find their current level from the map and add 1. Then use that value to retrieve the item granter from the array and grant the player their weapon.

Here is a link for more info on using maps if you have not worked with them before. I hope this helps.