i am about to buy the vise. i have the ff handguard,armorer wrench, browning armorer block,punch set. i am taking off my handguard and installing a ff handguard. i need to purchace some moly grease also. my question is this. once i get the barrel nut off, does the barrel come out? i know that i dont need to take it out, and i dont want to, but i am basically afraid of it coming out and then having to reinstall it. i have seen people talking about proper torque for the barrel, and that makes me nervous.

Unload your gun, all that.

Take the upper off, take the bolt carrier out.

Once you take the handguards off, you will have to use a punch to push out the pin that holds the gas tube (it's on the 'cross bar' part of the front sight).  Once that pin is out, the gas tube, which will be mostly stuck if you shoot much, will have to get worked loose.  Push it (the gas tube) back towards the upper until it's clear the front sight post, then rotate the tube so you can work it past the front sight and pull it forward towards the muzzle.  

Once the gas tube is out, you are free to wrench on your nut (barrel nut, of course).

Once the nut is off, the barrel is a slip-fit into the upper; no twisting, pulling or anything.  A short pin on top of the barrel fits in a slot to index it.  That's it.  Easy day.  It may come out, just slide it back in.  You can't put it in too far, or not far enough.  This part is pretty hard to screw up.

Put anti-seize (or grease, or whatever) on your threads before re-installing.  You may torque it to the specs in the TM, but there are those that say you only need to snug the barrel nut, not torque it, as the gas tube prevents in from unscrewing.  Make sure the holes in your new barrel nut line up and give your gas tube a straight shot to the gas key on the bolt carrier.  You may want to ask around as to what might be best for your situation.

eodinert, thank you. i was nervous about the indexing part. i have already took off the fsb, and all that, but found that i truly do NEED a vise for the block and upper, that there isnt a way to improvise without one. thats where i came to the barrel question. thank you.

buy or find a place to down load and read this book. TM 05538C/23/2

http://www.ar15.com/content/manuals/TM9-1005-319-23.pdfTM9-1005-319-23

a good place to get cheap moly grease is the auto parts store.  most of them sell it in small packets intended for lubing up the disc brake caliper rails.  i usually see them for around $1(done 6 uppers and still going strong  on the first packet).  if you buy moly grease from gun places get the jar of vasoline ready...ie way over priced.

Moly grease is also avalible at Wal-Mart in the auto section with all the other grease tubes for grease guns. Just over $1.  If the barel nut does not line up rite with the gas tube, you may have to file the front of the reciever some. (NOT MUCH! just bearly take the finish off with a 400 grit stone. I did one with 400 grit paper on a block.  Just a few leavel passes) I have had to do that with 2 so far. First if you have problems tighten it on, take it off, tighten it on, take it off, 3 times see if it lines up.  people argue on the torque needed or what is "proper" 30-80 usually.  Good luck and ask for help if needed.  God knows I have.         *James*

I improvised a tool.I used a center puch because the nose is already rounded.I rounded the point off so its a round smoothe top and then dremeled a trench that matches the U shaped nut notch.My armorers hammer and using a 2 inch piece of old gas tube to stop the spring and snap ring notch for the gas tube  from rotaing as the nut is tightened it works quite well.You put the gas tube part in the carrier key and insert the whole carrier.