All the clones, CETME's, and HK's are going to have fluted chambers, needed for the DRB action to operate.
Up to a point you can shoot lighter loads, but too light can get to be tricky, because the action is a blowback delayed by some tricky German engineering. There's a bolt head, bolt carrier, and what's called a locking piece sort of inside connecting the two other bolt parts. The locking piece has a wedge shaped nose that pushes the rollers out of the bolt head to lock the bolt to the bit that the barrel is pressed into. To shoot reduced loads, or standard loads with a longer barrel, you need a locking piece with less angle, that keeps the unlock timing correct with the bullet's position in the barrel.
How light is too light? I couldn't tell you, as I shoot factory loads of one sort or another.
The theory with ripping the brass apart does have to do with the flutes. Softer, thinner brass, and a hotter commercial load tends to push the brass into the flutes more than the designer planned for, causing more resistance to extraction. PTR had a model at one point that they said was engineered to function best with commercial loads - I suspect the flutes were larger, but I don't really know.
From what I read PTR remains one of the best deals around on this style rifle. As far as I know, most parts are interchangeable with German military. They also just announced a move to South Carolina from Connecticut - thanks entirely to the restrictive gun legislation passed in CT. I like companies that have principles and aren't afraid to make a point
PTR also makes one chambered for the little Ruskie 30 cal round, but I still think the rifle looks a bit goofy with an AK banana mag sticking out.
I've seen a pretty neat home made design for a bolt hold open. A bit tricky but not impossible. Of course the question with stuff like that is does it work thousands of times without fail, or just the six times the guy posts on his youtube video. I don't know of any commercial retrofits for it. You'd think PTR in particular would have done something, but I have to wonder if part of the reason why not is to stay compatible with the cheap surplus mags.
I don't know much about comparisons to other NATO caliber battle rifles, this one is the only one I've ever owned, everything else is a bolt or lever gun
I've read that the AR style is great with the 308 round. But then almost everything is great with the 308, it's a great round. I might even take a liking to AK's if someone built one in 308!
