During SHOT Show 2018, Anderson Manufacturing has introduced an AR-15 upper with a different muzzle device, gas block and handguard attachment systems as well as a built-in backup rear sight.
The muzzle device attachment system is similar to that of AK rifles. This system utilizes muzzle devices with AK-style fixation/alignment notches in the rear. There is also a separate collar with a built-in spring-loaded plunger. In order to install the muzzle device, you need to slip the collar over the threads, then screw the muzzle device and fix it via the plunger. The barrel has a flat surface cut right behind the muzzle threads which corresponds to the flat surface on the collar and keeps the whole assembly from rotating.
The advantage of this system is the possibility to quickly change the muzzle devices. A disadvantage is a need for special muzzle devices with the retention notches. However, I think if you have a muzzle device that you really want to use with this system, it should not be a difficult task for your local gunsmith to machine an alignment notch into your muzzle device.
Next up is the new gas block mounting system designed by Anderson Manufacturing. Right in front of the gas block portion, the barrel is threaded. In order to mount the gas block, you need to slip it over the barrel aligning the pre-installed gas tube, then install the provided lock nut thus tightening the gas block to the barrel shoulder. The latter also has a machined flat surface allowing to align the gas block consistently.
The handguard is also designed to consistently align in the same position. It is fixed in place by 4 screws.
This new Anderson Manufacturing upper receiver also has a built-in backup rear sight, which when folded fits flush with the top rail.