So far, I haven't seen a single SR25(.308). G&G has one, I'm sure you could gut it, and make it worth your time, might be a decent weapon.
Personally, I would stay away from any sniper rifle that isn't gas. I checked out Brian's(IcePlatinumSky) M700AICS...and its fantastic. Excellent range, consistant accuracy and shot placement, virtually no diffence in FPS between shots(Stayed a consitant 460 or so with .20s). I'm thinking about picking one up personally, but I don't know how much I would use it. I think I'll stick to being a regular rifleman.