I forgot to mention that this is for Single player so I'm not sure if you can run client commands in SP? And yes, you'd also have to turn cheats on and off again in order for that to work, but its definitely a possible hack if I can't get it working any other way.
You will most likely need to use a trigger_once on top of where the player spawns with an output like "Ontrigger>env_entity_maker>set parent >!activator" To make sure the entity maker gets parented to the player on the map spawn.
Why don't you just place the specific ammo type at the feet, he will pick it up automatically.. If you trying to do a timed thing like a dispenser or like a checkpoint then the entity make would work or client command
yeah, game_player_equip only works in MP and either at spawn time, or when the player "uses" it so it doesn't work for me. Didn't get a chance to try Omni's suggestion but I'll do it asap and let you know how it worked.
With my initial test, Omni's idea and smurftyours' suggestion of setting the parent to !activator doesn't seem to work. I'll probably need to play around with a setup in a stand along map to figure out definitively if it will work but I'm in crunch mode at the moment so it'll have to wait.