IMO a .410 is not a deer gun. Of course, deer can be killed with one. If the question was "Should I buy a .410 for deer hunting?" the answer is no.

If a person is limited to a .410, then I'd say limit the range to bowhunting ranges, like 40 yds and under, and take only broadside to quartering away shots at the heart/lung area.

I will shoot deer in the neck (I don't generally take a head shot), but wouldn't recommend it with a .410.