Ok, well, seeing as F.Rabshaw is being a jackass about this, I will tell you all how to do it since I managed to figure it out.
All you need to do is spawn as support, go somewhere, drop some ammo packs, kill yourself, spawn as assault go to the ammo packs and then start tossing your hooks, when you toss one you will immediatly pick up another from the ammo pack, and if you keep tossing and picking them up in succession it wont switch to another weapon, so all you need to do is hit fire and pickup back and forth.
All you need to do is spawn as support, go somewhere, drop some ammo packs, kill yourself, spawn as assault go to the ammo packs and then start tossing your hooks, when you toss one you will immediatly pick up another from the ammo pack, and if you keep tossing and picking them up in succession it wont switch to another weapon, so all you need to do is hit fire and pickup back and forth.