I shot a 716 DMR a few weeks ago.
Beautiful rifle, with top notch machining, fit/finish, etc. Everything. AFAIK, they're basically all Sig made (Sig has been outsourcing less and less), and all machined right here in NH. But I wouldn't pay retail for one. It's big, expensive, heavy, and a Remington 700 will outshoot it. No QC issues with them, there are just cheaper ways to accomplish what they do on a one-way range when you're just punching paper. Rifles like the 716 DMR are made to sit down groups of bad dudes shooting at you from behind walls/cover from hundreds of yards away.
I don't understand why you would buy a rifle like a 716 DMR to shoot Tula out of. That's like dumping the old tank of chainsaw gas you found in the garage into your brand new WRX STi. The barrels are guaranteed 0.5MOA or better, but that's with quality (read: expensive) ammo. The fact that it's piston driven really shouldn't affect whether or not it cycles crappy steel ammo anyways.
If your friend just wants a .308 battle rifle to blast paper and bowling pins at the 50yd range, I think the 716 DMR is way overkill, and a waste of money. Just buy any of the other cheaper 308 AR10 platform offerings out there. Or a FAL. If they have no problem spending a lot of extra money to get a top-notch rifle just because, then the 716 DMR is a great choice.