contact dedicated technologies, owned by an AR smith named Mike Milli, he has exclusive rights to build custom uppers (at almost production prices BTW) by Oly arms. He is a Oly service center so any upper built by him also carry's Oly's lifetime warranty. you'll find him at
dtech1@paulbunyan.net
RR
Oh almost forgot, mike built my 25 wssm, I'm quite happy with it.
edited to add: If you do not reload your better off with the 243 wssm, the 25 WSSM factory loads are too long for the mag with the exception of the 120 gr WW loading, even the 85 gr supremes are too long for an AR mag.