The Larue PredatAR has a free floating lightweight barrel in a proprietary upper with free floating hand guard.
The barrel is made in house, the barrel nut is 1 1/4 inch. The heat treating method that Larue Tactical uses gives it a golden, almost brass like color.
The upper and rail have mating surfaces to ensure alignment. 4 screws hold the rail to the upper, with helicoil(or similar) inserts.
So, why did I have this one apart? I was showing it to a friend expounding on how great Larue stuff is. When I got home, I was looking it over again and I noticed a very small amount in play in the barrel. After removing the hand guards I found the barrel nut was loose.
Now, even more annoying is that I don’t have a wrench in 1 1/4 inch size, I visited several local auto parts stores and hard ware stores and the half dozen stores I visited this weekend didn’t have a crowfoot wrench in that size.
Goes to show that no matter what your equipment, you need to inspect it regularly and have spare or backups.