AS I remember those items were solid object not model. If they are solid items they can be tied(turned to) to func_trains that move at the same speed of the convoyer, when they are out of sight they teleport to the starting point. The convoyer's push only affect the player and monster it doesn't affect solid objects or items.
I'll tell you what you can do, it's quite more complicated to do so with weapons or items but possible. Does the armory entity have a 'children's name' value, or 'name of the spawned item' value? I don't mean the actuall name of the gun, I mean names you give entities. If it has then what I have in mind can be done, otherwise it can't.
The armory entity should be above a small, invisible but a solid func_train, but it must not touch it the train. At the begining of the round it should be activated by a trigger, is the trigger_auto activated at the start of each round? If not use a trigger_relay instead and the auto and give it the name of game_playerspawn, use it to target the armory. The trigger_relay will activate the armory each time the players spawn, or in other words each round. I don't know if fy maps have rounds but if they don't just use a trigger_auto to trigger the aromry, it will trigger it when the map loads.
The trains first path corner(right below the armory) will have the teleport flag checked and in the fire on pass write the name of the armory entity. The train will move toward the other end with the gun on it, the gun will follow it. In the last pass_corner's fire on pass value write the name of a diffrent trigger_relay. In the trigger_relay write the name of the gun entity, thats why it's important that you'll be able to give it a name, like in a monstermaker, the trigger_relay will delete the gun. If it wont delete it then the guns will pile up at the last path_corner!
By the way, you cannot have the armory spawning weapons for more then one train unless you want some to disapear before they reached the train. On armory entity for each train, all of the trains and armories need this setup, and with diffrent names for each entity.
This will work for sure, unless the armory has no children's name value.
Edit:
Rotorsplint, this is obviously for CS 1.6, trigger_push wont work in this case, nither will the convoyer's push.
Edit #2:
If you do want them to pile up at the end of the line, you don't need the second trigger relay and giving the weapons names. Although I must warn you that it'll look like there is only one weapon when there can be thousand of them, weapons aren't solid you can't place other weapons above them.