How can i make a good collision for a barrel?

I need it to be hallow so i can put stuff in it and to respond to physics as well .
When i try to make an UCX_NameOfMesh with a hole in it, it gives me a result of colorful collider with blue and red and such ( Which is not good i supposed… ) and then when i test it it harming the performance dearly .
I’v also tried several UCX_NameOfMesh_0# and it gaves me something even worse, so, how can i make it work ?