From MDT site, should be solid in XRS.
Each XRS Chassis is constructed from a full-length CNC machined core of 6061 aircraft grade aluminum wearing high strength textured polymer panels for insulation from the elements.
Ya, I agree and it certainly feels solid.
I have seen some blow up expansions of the XRS and its a bit unclear if the aluminum block extends through the last portion of the stock. Certainly through the grip but beyond that I don't know. I cant post pictures here but it can be googled.
As I say, it feels really solid but I haven't shot it with anything heavy in it. I was just comparing it to the ESS which is clearly aluminum tip to tail. I imagine it is twice the cost for a reason.
I should have added that it feels way more solid than the Magpul Hunter I used to have and I did shoot that under a 308. I noticed nothing at all in that platform and the MDT XRS feels like a step or three up from that in its construction.
I'm a big fan and I sure hope they are working on one to fit a SAKO 85 S !!