Scaling a box to fit a mesh?

Hi! Thanks for your answer but this is not exactly how I have it set up, (which I should have clarified earlier).

The changing mesh Is a childactor component, which is parented to the box.
image

Another thing is that I am adding a little push whenever one of these blueprints spawn, so I cant have any simple collision on the staticmesh that is in the childactor. (Otherwise it will also have weight and it will glitch out and fly away)