This is the upper from the first AR I ever bought, and paid way too much for a few years ago ...

I am told it is a Hart barrel of some type, and that they are in the ~400-500 range, and Hart's website roughly says the same thing.   However, I have been able to find next to no other information about this barrel, all I know is that it is 1/9.  I don't know what it is made of or if it is chrome lined.

This upper came with a POS Yankee Hill rail on it, one of the old models that was a single piece instead of being a 2 piece design.  I could rant all day about how much YHM rails suck, how they don't meet spec, how tangodown grips have to be carved out for them to fit, how entire rail pieces just chip off, how they have nothing to keep them from rotating off, etc, but I will let it go.

Anyways, I am trying to right the wrongs of whoever it was that built this rifle.  Why anyone would buy a "premium" barrel and cover it with the shittiest rail out is beyond me.

I am looking to put on a LaRue to DD lite rail, 12 or 13.2 inches, and I have no idea what to do from here.  My other rifle is a LMT m4gery, and I have the Troy MRF-CX on it ... to get this on, I dremeled off the delta ring assembly to get down to the factory barrel nut, which the Troy rail clamps to.

The problem is, I have no idea what this big threaded POS is, or if there is even a barrel nut underneath it.  Furthermore, I beleive I have to remove the gas block in order to install a DD lite or LaRue rail, and it simply refuses to move.  I took out the two screws you see in the picture, tried heating it up, and ultimately got pissed and went at it with a hammer.  No movement.  Is this thing somehow permanently attached?  It seems idiotic, but I don't know why it won't move.

So my question is, what do I do about my current gas block/YHM big threaded circle thing.  Is there a barrel nut underneath that, or wtf?

I have never built an upper, only lowers, so this is new ground to me.  I would love a chance to remove a barrel and install a free float rail that isn't a Troy, as I feel my hands on experience has a big gap in it, that gap being the barrel seating process.  

Anyone help?  What should I do?  Does the Larue come with something to replace this thing?  Can I just dremel it off?  How do I get my gas tube out of there?

The gas block looks like a YHM block. SOmeone may have used loctite on the block and or the set screws raised some burrs on the barrel when they were tightened causing it stick in place.
There are several ways to get it off. All could damage the barrel and block if you are not careful.
If you can remove the gas tube and heat up the block to maybe about 300 to 350 degrees which is where loctite melts (if there is any on it) and it will also expand the metal a little then you can use a piece of wood and a hammer to tap the barrel off. Place the muzzle with a flash hider or brake on it to protect the crown then place that on some wood on the floor. Have a buddy hold the thing while you have at the block with preffebly a hardwood dowel and hammer. With out the gas tube there that will give you a larger area to tap against.
Another way is to cut it off but you might cut into the barrel if not really careful.
You could also close a vise till it just catches on the block (you will damage the block with this method) and tap against the muzzle with something screwed on to protect the crown. Of course you can damage the threads if you go at it too hard along with scratching the barrel up if you don't tape it up.
Heat will help in this also.

The block most likely wont fit under any of the rails you want to run as it looks pretty bulky so it is no big loss if it gets banged up some.

To remove the gas tube you need to use a punch and remove the roll pin that is in the home on top towards the back. Then the tube might slide out or might be stuck due to a tight fit and or carbon build up. with the carrier out pull straight back on it and it should slide out.

The big round thing is the barrel nut. It will be replaced by a different style with the DD or LaRue. You will need a free float style barrel wrench to get it off. DPMS makes a wrench that will do both mil spec nuts and free float tubes. You will also need something to hold the receiver like the clam sheel receiver blocks or barrel clamps.

One other thing is you don't mention a muzzle attachment. Is there one and is it permanetly mounted?

If you don't have any I would suggest sending it off or finding someone near by that has the tools to help you out. It isn't hard to swap barrels and uppers if you have the tools but they will run about 75 to 100 bucks on up.

I have an A2 flash suppressor that is currently off of it. I want to put an F2 brake on it. That is not an issue.

I'll try heating it up again and banging it off, but as I remember it really did not want to move.

You're telling me the gas tube comes out the back of the receiver? I don't see any punch to remove to allow this to come out. Where is this located? "In the home on top towards the back"?

Once I somehow get the gas tube out, and the gas block off, I then use a free float wrench to unscew the barrel from the receiver? While the receiver is being held in a receiver block?

I'm looking into these parts right now.

I'm told the Bushmaster makes the best action block on the market ...

Bushy action block

Yet it is not available at Rainier or Denny's ... and I have a stigma about ordering direct.

Is this one comparable, or nearly as good?  I can't tell if the bushmaster one is made of metal, but this one is "rynite".

Rainier action block

For a barrel wrench, this one is one of the best, right?  It looks just like the olympic arms one, it may even BE the olympic arms one ...

Rainier barrel wrench

I also don't really have a good metal vise ...

I've gotten the gas tube most all of the way out, I can now see half of the whole that the drift goes through ... at this point, it has decided to stop movement, and I do not have man enough pliers to convince it to do otherwise.

I completely mangled the gas tube by brute forcing it out with teethed wire cutters, which is all I really have available, sadly.  

Anyone have any suggestions as to what I should look for in a metal vise, or specific models I should look at? I need to get one of these.

Other than that, Adco and rainier seem to have all the tools I need, unless someone knows of another source for that Bushmaster action block.

Thanks for the help in advance.  It feels good to be rounding out my AR building knowledge.

Quoted: I have an A2 flash suppressor that is currently off of it. I want to put an F2 brake on it. That is not an issue. I'll try heating it up again and banging it off, but as I remember it really did not want to move. You're telling me the gas tube comes out the back of the receiver? I don't see any punch to remove to allow this to come out. Where is this located? "In the home on top towards the back"? Once I somehow get the gas tube out, and the gas block off, I then use a free float wrench to unscew the barrel from the receiver? While the receiver is being held in a receiver block? I'm looking into these parts right now.

On the gas block there is the hole on the side on top. Inside the hole is a roll pin that holds the gas tube in. Punch the pin out. The the tube slides towards the back of the receiver until it coes out of the block, then you pull it forwards.

The rest you have correct about the nut.

Quoted: I'm told the Bushmaster makes the best action block on the market ... Bushy action block Yet it is not available at Rainier or Denny's ... and I have a stigma about ordering direct. Is this one comparable, or nearly as good?  I can't tell if the bushmaster one is made of metal, but this one is "rynite". Rainier action block For a barrel wrench, this one is one of the best, right?  It looks just like the olympic arms one, it may even BE the olympic arms one ... Rainier barrel wrench I also don't really have a good metal vise ...

Ok this new format is really pissing me off since I can't read all the replys and answer them.

The rainer block is correct but the wrench lacks the free float tube portion to remove your free float nut.

Quoted: I've gotten the gas tube most all of the way out, I can now see half of the whole that the drift goes through ... at this point, it has decided to stop movement, and I do not have man enough pliers to convince it to do otherwise. I completely mangled the gas tube by brute forcing it out with teethed wire cutters, which is all I really have available, sadly.   Anyone have any suggestions as to what I should look for in a metal vise, or specific models I should look at? I need to get one of these. Other than that, Adco and rainier seem to have all the tools I need, unless someone knows of another source for that Bushmaster action block. Thanks for the help in advance.  It feels good to be rounding out my AR building knowledge.

Ouch, pliers? mangled? Not saying this to me a jerk but you should pick up a copy of the army or marine Technical manual that covers the AR/M16 for starters. It will help you with specs and drawings to show what goes where and how tight to make it.
www.brownells.com/Default.aspx  carries all the tools you need. They might be a few bucks more but since you can get them all at one place you save on shipping.

The gas tube can be a pain to get out as carbon does make them stick some times. They make a tool to get it out with out crushing it.
A 4 inch or larger bench vise will work for the AR action blocks. I bought one at lowels just cause it was handy. Cost 40 bucks. Any home improvment store will have something that will work.  Yeah, it is made in china but what isnt these days. A good wilton vise is nice and US made but not worth the bucks to rust away sitting in outside.

Heh.

I can fully understand that.

However, I like doing things myself, as do many others.  Not only does it give you a ton more experience and understanding, but it allows you to work on other rifles and projects in the future.  There is an attraction to being self sufficient :)

I now need 5 items to finish this project.  

I started a new thread trying to find sources for these 5 things here ....

5 things I still need

Thank you for the help everyone.