They are one in the same. The 40x is supposed to be held to tighter tolerences, however I have seen some 40x's that didn't shoot for crap. This had to do mainly with the barrel, it seems Remington has gotten pretty sloppy with their chambers. IMHO I would save the extra cash and go with the 700 action and get it squared and lapped, usually the 40x actions cost quite a bit more.