Jeff Munnell wrote an article, "Some Other Eight Millimeter European Sporting Rounds" in Precision Shooting magazine, November 2005. Page 75 and 76 describe the 8x60 and 8x60R in both J and S versions, (i.e. all 4 variations). He states, (from experience), "the rimmed versions can similarly be formed from the common 7x65R or the more expensive 9,3x74R". He had an un-named break-open single shot specifically marked 8x60RM which, although there was no "S" designation, was .323" bore. Using IMR 4064 and a 200-grain Speer spitzer, (.323" Dia.), he was getting 2,754fps from a 28,1/2" barrel - and sub 1" groups at 50 yards using open sights. His used a small supply of RWS factory brass for this. This factory ammo chronographed at 2,759fps. He used #5260 primers throughout his testing. He also describes loads for his 8x60 rimless rifles.