I think CAYUGAD's Black Diamond is the XR. I think hehassuccessfully usedstandard Winchester & Remington Kleenbore primers in it. That rifle does real well with the #11 cap attachment also using the RWS/Dynamit Noble 1075 percussion caps.

Lots & lots of sabot grain combos can be used in that rifle. The ultimate grain sizes are between 240-370 grains from what I've read. I think CAYUGAD has-had good success with No Excuse 460 gr. conicals also. But I do not know if that diameter is the .500s or the .503s???

Whichdiameter has Dave from No Excuse Bullets sent you Mr. Cayugad? I may buy some this spring.