A 12 ga slug gun shooting standard rifled slugs. That is one of the few things I think you could actually shoot through brush that might not deflect too badly or deform the bullet too much. It is pretty much just a big heavy slow chunk of lead. I still wouldn't suggest shooting through a bush or something with one.

I agree with the others, when I think brush or woods gun I think of something that is quick handling and is designed for shorter range shooting. Like a carbine with a low powered scope or open sights.

As far as shooting through brush with a gun I think that might depend more on bullet choice than it would caliber to an extent. There are some bullets that would handle it better than others. Then again you would give up expansion on game to achieve this.

Paul