Brush gun
I think the original question referred to what calibre/bullet would best go through brush to kill an animal seen screened through the brush. Unfortunately, not many of us could answer that question from experience. We may have killed an animal with one shot, when it was screened behind brushy bush. If so, then the calibre/bullet used will be the best there is!
However, we may have been lucky, the bullet may have gone between significant sized twigs.
I have read where more than one gun writer has set up targets behind brush and blazed away. The results I have seen were that calibre/bullet didn't make a great deal of difference. It appeared a 45-70, or similar, didn't do any better than a 308/30-06. I think they even mentioned a 243, but I couldn't swear to it. Of course, we know a lightly built bullet, whether a 243 or 270, will break up after hitting almost nothing in the way of brush. I think the test was for normal hunting bullets usually used.