The barrels don't accelerate under the force of gravity correctly. The physics sucks.
There's a reason for that....
" Its funny you mention that because at first thats exactly what they did, but I had issues where the barrels at the top would pick up so much speed that they'd ignite a huge explosion force to the pile of barrels causing them to fly thoughsands of feet away, I had to give the barrels a max velocity for that specific reason aswell as to have them fall slower then I was. "