Ballast tube Brainwave

Having never seen a ballast tube in the flesh I have no idea  how the ballast shots and packers are secured in the tube. But late last night I came up with this idea and implemented it this morning whilst the Family popped down the road to see the Olympic Torch travel from Mumbles to Swansea.

It's the same principle as a rifle loading mechanism or for the less agressive an ordinary shoot bolt

The elastic band keeps the latch in place