Playing On The Rails, I found that on one of the carts (it’s likely all of them, as they share a model), there is a very large gap that can’t be shot through.
It’s where my crosshair is, and on the other parts similar to that on the cart.
Founded in 2004, Leakfree.org became one of the first online communities dedicated to Valve’s Source engine development. It is more famously known for the formation of Black Mesa: Source under the 'Leakfree Modification Team' handle in September 2004.