Maybe you're right 93x64. I have the same rifle, bit fancier, also with a LOP suited to a giant. Mine is also chambered in an Eley calibre, this time Eley 280 Rimless. That's the designation on the rifle. Beats me what round that is. It's not the 280 Rimless aka 280 Ross. I shoot several Ross sporters and have 1960's Kynoch factory ammo - the Lancaster won't digest the rim on that. Seeing the gun above,which would be a nice sibling for mine, it reminded me about this weird ammo designation.