Hi bonanza

There is in deed a difference between 8x57IR and 8x57IRS. The 8x57IR is the rimmed version of the older 8x57I ( "I" for "Infantrie", "R" means "rimmed" ), once the standard military round M88 of the German army, which was modernized in 1905 and since then there are two almost identical 8mm calibers on the market. The S-calibers have a slightly larger bullet/bore diameter ( .323 ) compared to the older rounds ( .318 ), which is not only confusing but forbids using the newer 8x57IRS in the old guns chambered for 8x57IR, excessive pressure would result.

Regarding reloading there is first the problem to find bullets in .318 diameter for the old cartridge, here we have the choice between a 196 grains round-nose from RWS or Sellier and Bellot ( Czech made ).
Dies for the 8x57I are available from RCBS and can be used for the rimmed version as well, but be prepared to pay a premium price.
In a pinch, You could use a 8x57IS die without the expander,otherwise the bullet would be loose in the neck.
Cases are available ( at least here in Germany ) from RWS, but 8x57IRS cases can be used without problems, as long as You don`t get confused with the head stamp.

Kalunga