I found a shell casing this morning ata pit that I shoot at , it looked sort of familiar untill I picked it up. I took it home and started measuring it out with the calipers and here is what I came out with. It appears to be the same dementions as the RSUM but the shoulder has been pushed back from the standard 1.538 to 1.450 , and it looks to have a 35deg shoulder. The case neck is .295 on the outside which leads me to think its some sort of 6.5 Wildcat. The parent case is a 300WSM by Norma. Any of you cartridge makers out their ever heard of such an animal ? It seems to me that the case capacity would be close to what the 6.5x284 is maybe a little bit more.