Lumicreative.com ah yeah I was suggesting a slightly more intensive solution, which is to basically replace the bullet behaviour with raycasting. I think in your example is a little broken, with some tweaks it would probably work after a fashion. But under some circumstances it would fail, when passing near to an object the center of the ball may not pass through a box, but the ball would overlap with the box. In that situation the raycast would never report a collision, but the bullet behaviour would.
This is your project adapted to what I meant. It works well, but it will occasionally not collide when it appears to due to being considered a particle. Using a smaller ball makes it look more convincing. There's some tricks you can do to simulate the ball as a polygon, but you end up back with the problem of flat edges vs curved.
You can kind of do collision with other ball instances, but it causes some strange collisions because we have a single position buffer which we are read/writing to at the same time.
I was thinking you could also solve this using signed distance fields and raymarching ( subtly different to what the LOS plugin uses ) but you would basically have to write all this logic from scratch.