Do you roll 2 dv against a barrier 10 times, or 20 dv once? I have no idea.

one time, just like any other attack. and just like any other attack, if the modified damage (without the autofire modification) do not go past the modified armor rating, nothing happens...

It says "2 DV per bullet" for a reason...

ye gods, i seriously had missed that table there...

sorry about that mixup

hmm, looks like the best bet for bringing down a wall is explosives, melee damage from a troll (preferably wielding a gigantic sledgehammer) or a spell of some kind. bullets and other projectile will not have an effect unless your going for belts of it

So bullets are worthless against a good barrier... got it.

I really like how SR4 handles barries from prior versions. This gives concrete (no pun intended ) rules for doing all the things runners want to do to them.

Good question hobgoblin, thanks.

But if the 2DV plus net hits aren't good enough to puncture the barrier rating, nothing gets through when trying to destroy the barrier, right?

The way it's written, who knows? It's totally unclear about it. The listed DV is figured out as "2 per bullet," as opposed to "2+autofire mods," so there's really no good way to determine what you're supposed to do.