Your Browser is Outdated
That will depend on the muzzle device. In general you will want to stay shorter than 13.5" but if you have a blast shield or a linear compensator, you should be able to use a longer handguard up to 15".
The barrel with MPN: 15A58M16NPQ-IMDB is the pencil profile barrel and the barrel with MPN: 15A58M16NGQ-IMDB is the Gunner profile. It does appear that the Optics Planet description lists "Gunner" for both, but the one with "P" in the part number is the Pencil profile.
The barrel will work with any standar AR-15 barrel nut. Most modern free float handguards will come with the required barrel nut.
This barrel will require a mid-length gas tube.
We cannot speak to the deals and promotions that Optics Planet runs on our product. The above barrel does have a muzzle device built in so while an additional muzzle device wouldn't be needed for this barrel, perhaps it could be used on a future build.
No, the muzzle device is milled into the end of the barrel so it is one solid piece of steel. This gives you the same overall length as a 14.5" barrel with a pinned and welded muzzle device, while being stronger and lighter.
No, this listing is just for the barrel itself. This particular barrel has a muzzle brake milled into the end so you would not need to purchase a separate muzzle device. You would need to purchase a gas block, gas tube, and barrel nut separately.