As I understand it the Royal Marines have acquired a number of 6.5cm AR10 type rifles. Because of the high BC bullets with better long range performance than 7.62 NATO the operators of military ranges have thrown a hissy fit about how dangerous 6.5cm is and how much greater a danger area envelope they require and they are uncertain as to whether they fit into 300 win mag or 338 Lapua as used in the sniper rifles. Hence there is a ban on use of 6.5 cm on military ranges (most pf which are run by private sector companies) until the full ballistic envelope is worked out. Many clubs also shoot on these ranges, hence ban applies to them as well.
Of course, given all the hype over the 6.5cm and its long range performance, the powers that be are absolutely correct in this course of action.
Many clubs also have ranges, especially the indoor type ones that are built for 22 lr and pistol calibre type cartridges. They don’t have target backstops suitable for full bore cartridges.