Juggler...
Make special ammo a rare event like heavy ammo but also make it obtainable by getting kills with your primary weapon equipped like juggler.
Only you can get the ammo dropped from enemies you kill, instead of team wide.
All ammo is lost on death.
This would promote primary weapon usage and be a reward for doing well. If you started using your special weapon though ammo wouldn't be dropping for you.
Thoughts?
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Maybe
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