To get multiple free tags from a thaumaturgy maneuver, you need to pile up aspects. This is done by adding copies of the same or very similar aspect.
YS:265
If the intent is to create a temporary aspect
that can be tagged more than once (remember
that normally you’d only get the benefit of the
tag once and have to invoke after that), simply
chain two or more maneuvers together in the
same spell, each inflicting the same aspect or a
similar variant. In other words, if you want to
take advantage of two tags against a target of
Good Conviction, you’ll need to set up two
maneuvers, for a minimum complexity of 6 (3
for each, as per above).
So, to enchant 5 Bullets (which really is nothing more than getting more free tags), you need 15 shifts.
Keep in mind that those aspects only stay for a limited amount of time. Without added duration, they'd be gone after 5 rounds. whether you use them or not.
So realistically you can enchant 2, maybe 3 bullets on the fly without to much trouble. Anything more would pose major problems at evocation speeds and methods.
Then again, you need to take hexing into account... putting magicked bullets into a fancy gun could get ugly.