Larger Rounds
We used to refer to the SLR as the elephant gun, because it would literally stop an elephant in its tracks. The entrance wound would be small and the exit wound would be massive. Talk about being affective!!
However, the russions were, at the time, using 7.62 rounds as well, except their rounds had grooves in them. Consequently, our rounds, would fit into their weapons, but their rounds would not fit into ours. Simple, but quite clever really.
The 5.56 round was introduced to rattle around inside a body, so that if someone broke from cover to help an injured colleague they would get one too.
The good thing about the SA80's reinvention was that the introduced the SUST site with it, unlike the SUIT Site from the SLR days, they finally got the sight needle the right way up.
Cheers
Steve