I know an ex Royal Marine who told me a lot about this rifle, I forget most of it, had a play with one at Plymouth one day in the early 1990s.
I recall thery were not popular as they need a battery for the sight I think. They were used in the Falklands (unofficially I think) and they sent the wrong batteries so it was a huge cock up.
I used the SLR 7.62 and it was a heavy bastard compared tp the Steyr. The Steyr had its own problems early on, the plastic parts were melting, it was considered a piece of shit compared to the SLR. It also upset a lot of traditionalists as we had to change how we marched. No more shoulder arms when marching, now its this girly method of holding it when marching.
At least you could belt the fuck out of someone with the SLR and do some damage and it had good reach with the bayonet.