Since the length is 5.5 inches and 4 inches cover your barrel, your barrel will be 18.5" if this is pinned.
The Guntec USA AR .308 Cal Slip Over Barrel Shroud w/Multi Port Muzzle Brake covers 4" of the barrel so you will need a handguard that has an internal diameter of 1.2" or larger if it is less than 4" from the muzzle.
The Guntec USA AR .308 Cal Slip Over Barrel Shroud covers up 4" of your barrel, which would interfere with the gas block on the 716i Tread. Making it not compatible.
The Guntec USA AR .308 Cal Slip Over Barrel Shroud fits directly to a 5/8x24 threaded barrel. If you have a muzzle device equipped, it must be removed in order to install this shroud.
The Guntec USA AR .308 Cal Slip Over Barrel Shroud w/Multi Port Muzzle Brake might work with that barrel if it is threaded for 5/8x24. However, the manufacturer does not state what is the maximum diameter barrel the Guntec USA AR .308 Cal Slip Over Barrel Shroud w/Multi Port Muzzle Brake is compatible with, so I recommend contacting the manufacturer to confirm compatibility.
The Guntec USA AR .308 Cal Slip Over Barrel Shroud w/Multi Port Muzzle Brake does not to be timed and can be hand tightened to your threads. Some lock-tite would ensure the barrel shroud stays in place.
Yes it can.
The Guntec USA AR .308 Cal Slip Over Barrel Shroud w/Multi Port Muzzle Brake covers 4" of your barrel. Measure your barrel to ensure the gas block will not interfere with this barrel shroud.
The Guntec USA AR .308 Cal Slip Over Barrel Shroud w/Multi Port Muzzle Brake cannot be shipped to Canada. The export policy can be viewed below.
https://www.opticsplanet.com/export.html
Yes. I believe the Diamondback 300 acc Blackout rifles use 5/8x24 threads, and would therefore be able to fit the Guntec USA AR .308 Cal Slip Over Barrel Shroud and muzzle brake.