[Magnum88C]

I'd rather go with a dedicated rifle for such a beast.

For SHTF, they would be very useful in point defense, you wouldn't carry it as an MBR.
The problem, however, is not just the bulk and weight of ammo, but the extreme cost of the ammo.

 

[Magnum88C]

4. Even if you DO get a shot on a liquid fuel rocket, do you know the design to identify where the fuel tank is?

Mike

Not to mention you'd have to hit the tank RIGHT. A glancing hit, even from a .50 will not rupture the pressure vessel. So you'd have to know where the tank(s) are, hit the aeroshell dead on, so it won't deflect the bullet, and then hope to hell an internal structural member doesn't deflect the bullet further. And supposedly do this at a mile. Give it up.