A Vickers Machine Gun was issued with a spare parts box and amongst the (many) components in that box were two spare feedblock mechanisms. The feedblock is the part of the gun that pulls the belt of cartridges through the weapon and offers the rounds up in the correct position to be extracted and moved into the chamber ready for firing. The feed mechanism on the Vickers is built around a heavy brass casting that slots into the front of the receiver immediately above the chamber:The most obvious feature here is the large ‘mouth’ and it is into this the belt and cartridges are fed:A pawl on the inside of the feed mechanism grabs the cartridges and mechanically advances them one at a time. You can see the two arms poking down here:The cartridges are presented, rim first, at the back of the feed mechanism ready to be extracted from the belt and passed down into the breach of the gun:The whole feed block is actuated by a rotating arm on the base that connects up to the rest of the mechanism inside the Vickers, which can be seen on the right of this view of the underside of the feedblock:This feedblock is a later example- originally they were made of steel but this was found to corrode too easily so it was switched to brass. This block is an insanely difficult piece of machining and must have taken many operations to mill out of a solid piece of brass. When you consider each weapon needed at least three of them to cover the one on the gun and two spares it is easy to see why Vickers guns were so expensive!