Question: what is the difference in shotgun cartridges?
Answer: Most old English shotguns have a 2.5” chamber, European-made cartridges are measured in mm so the equivalent is 65mm. Modern shotguns typically have a 3” chamber (76.2mm) so will happily take 70mm cartridges. You can shoot a 65mm cartridge in a 70mm chamber, but you cannot shoot a 70mm cartridge in a 65mm chamber.