I now appreciate that the Muzzle-Energy graph we were supplied with was probably incorrect, (Thanks Mike R !) so to clarify the position I’ve taken this from the NRA website re limitations at Bisley and on most MoD Ranges, including Sealand.
a maximum muzzle velocity of 1000 m/s (3280 ft/s) and
a maximum muzzle energy of 4500 J (3319 ft lb);
Cartridges which, when normally loaded, would exceed the ME/MV limits of any specific range may not be used on that range even if downloaded.
(Furthermore, the MoD have also banned the use of ammunition using copper bullets (or bullets made from similar materiels) as they do not deform in such a way as reduces the risk of ricochet.)
This is not something we wanted (neither did the NRA) but it is what we are lumbered with. Please ensure that your ammunition conforms – all the ammunition we supply does.