I am building a new upper and due to the lack of tools I am going to have a smith do the barrel ff tube install.  But I'm curious about the way it goes together.  Can anyone explain it?  Does the FF tube replace the barrel nut?  Thanks for any input.

Yes, the FF tube replaces the nut.  

You can do this yourself.  

Once you have all your parts, lay them out and you'll see how it goes together.  I did a RRA upper to a Colt 1/7 barrel.  I cut a channel slightly smaller than the barrel width in two pieces of 1x4 scrap oak pallet, put them in a vise, clamped the barrel in them and tightened the FF grips by hand to about 25 ft lbs, lined up the gas tube and pinned it.  It functions flawlessly and is my current favorite evil rifle.  

If you are in a hurry, it's probably a 5 min job.  You may want to use an oil filter strap wrench if you feel more torque is required.  I didn't even use the DPMS wrench I bought to tighten my HGs.

I just got my shorty RR FF HGs w/picatinny rails for my AWB sunset rifle build, and this is not a one piece affair like the Bushy FF I installed on my 20" barrel.  It looks like it will require a spanner wrench, but I'm not sure until I get the rest of my parts and assemble them.


Jim

Thanks for the input Jim.