And politicians do math like this:
If we sold 1,000,000 bullets last year, and we tax them at 10cents each, we'll get $100,000 this year!
Um, no. Because no one will buy bullets in your area anymore. And since they are out of town, buying ammo, they'll probably do some shopping while they're out there (so you lose more sales tax).
The UPS guy in that area will be pissed about having to lug all that lead around everyday, from the Internet sales!