How close to Military specs. does it come,steels used etc.How would it compare to LWRC or LMT for durablity.What would your opinion be on how it should hold up to heavy use and round count.

The only military piston/rod 7.62 in use that I am aware of is the reissued M14s' and M240....

I have a 716, and had a KAC SR25.  I sold my 2nd 716 and SR25 and kept one 716 for myself.  (Damn near paid off the house!)

Accurate, fantastic fit/finish, annodizing is hard and smooth, and not picky on blammo.  Handled the LMT and it seemed...okay.  Got/kept the SIG.

LWRC rifles in 5.56 are unreal, so I imagine the 7.62 version is nice too.

Durability SIG gets the nod.  Best "Quality" 7.62 AR ergo rifle in bang for the buck land.

I am a Colt snob though, and would have really like to handle/purchased a M901.