The British Army’s pamphlet on the SA80 rifle includes guidance on the different ammunition that can be used with the rifle, including drill rounds which are described as:
Drill — Either a silver coloured grooved case, a copper jacketed bul¬let and no percussion cap or solid machined single piece round all silver in colour.
Drill rounds are used to safely work the rifle with no danger of an accidental discharge. They are completely inert and frequently used in training. This illustration from the same pamphlet shows them being used to demonstrate a speed loader:
The 5.56mm drill rounds have silver cases with a copper round at the top:
A deep groove down the case sides to allow it to be identified as a drill round just by touch:
The headstamps indicate that it was produced by the Royal Ordnance Factory, Radway Green in 1988:
Drill rounds are also used by cadets to practice magazine loading, as illustrated in this extract from their guidance on weapons training: