The arms fit the dimensions of the barrel perfectly
You wouldn't trust a measly human to load barrels full of Gamma Radiation now would you.
Fourth Wall Commentary.
There was a wheel piece under the Leg but since it wouldn't balance just use your imagination.
If you want to know what the wheel piece is go to lego.com/pickabrick and go under technic and look for a 1/2 Bushel. Just think of the wheel as retracted.
The one mistake I made with this moc is that a put an vent on the gamma radiation container.