Has anybody had any experience with it?? I can't find much information about it anywhere.

Never heard of it myself. I know I read an artical by the WW engineers that tried to neck the 300 WSM down to 25 and 6.5. It wouldn't work to theur satifaction and they setteled on the WSSM for the smaller calibers. Something about excess pressure. NOW thats just what the artical said and thats beyond my area of expertise and expierence.

I've seen a lot of posting on various sites about necking down for a 25WSM.I have actually seen 1 semi-custom 25WSM but didn't have a chance to talk to the guy who owned it. I've also seen itcalled a 257WSM and 25-300WSM.
I haven't seen anything on a 6mmWSM.

I have built both .25 WSM's and a 6.5 WSM. The former turned out to be too much of a good thing - at least with powders currently available. The 6.5 WSM wasn't too bad - it gave velocities a plateau above the .264 Winchester Mag and produced standard deviations within an acceptable variation - using RL25. The 6MM WSM is going to be a barrel eating machine; and I would be surprised if it produced speeds much higher than the 6MM-284, which I consider to be the biggest case practical for this bore diameter.

I have talked to people using the 25wsm and they are pleased with the cartridge.It produces velocities comparable to the 257wby.I don't know of anyone with a 6mmwsm

I have only saw the reloading dies listed in Graf and Sons Inc. So thats as much as I know, it just sounded like a pretty kick ass caliber. They have a bunch of cool calibers listed. I was also thinking about the 22-243, not sure though.

My issue with the .25 WSM has to do with wide SD's of velocity and somewhat mediocre accuracy. Speed was at least as good as the .257 WBY - consistency is not.

I saw some very impressive groups fired with the 25wsm.Like everything else,I guess it is just finding the right recipe.

The middlestead is a wild round. My gunsmith builds them. He buys barrels with fast twist and was pushing some pretty heavy 22 bullets out at 4000fps. Sounds like he is only getting 800rounds per a barrel however.

well, I don't know if it helps, but a I have a 6mm-06. I sort of use 240 weatherby load data. I like 48 gr of imr4831 with a variety a bullets in the 70-80 range. You are right. It is hard finding good data for such calibers.