You can:
Give 180 SMG to a Cadet/Freecop
For such situations like drive-bying.
The Cadet/Freecop could buy more, if they're low on ammo.
Or once their 180 given SMG runs out, and you need to drive-by
you could stop and refill them.
You can't:
Give 180 SMG, Then re-duty, give them 180 again, and re-duty etc.. - Script abuse
I would say; You're safe to give a Cadet/Freecop some SMG/MP5 if they know the Drive-by laws etc;
You can shoot SMG if you're being shot etc, Suspects running, Drive-bying a car, Drive-by a person on foot ONLY if they're directly shooting you, Do not shoot running/idle suspects on foot.. Etc.
I'm not completely sure on giving one bullet, I guess that is more of a Scripters answer and/or someone who has came across the situation, or has gained information on it.