The Czech RM-70 MLRS was introduced in 1971 as a heavier version of the BM-21.
40 barrels firing 122mm (4.8″) rockets over 400km (250 miles), it was used by Czechoslovakia (and the Czech Republic and Slovakia after the collapse), Poland, East Germany, Libya, Finland, Angola, Zimbabwe and as recent as 2008 used by Georgia in the South Ossetia war.
I think someone has confused the road range of the vehicle with the range of the rocket.
This reminds me of a US account of the Falklands War, which described the 105mm Light Gun as having a range of 17,000 km. If that were true one wonders why bother to take them to the Falklands, when they could have conducted fire missions from Larkhill, but perhaps the time of flight would have been excessive.