Can this be done on an AR build?

Sounds like you may be checking out the wrong places online. Go surf to www.midwayusa.com and then www.brownells.com and check out their offerings.

Generally - the disapaitor is simply the carbine barrel with the full size handguards and furniture...... but it is not that easy The 'problem' - is where the gas block goes. Carbine and standard have the gas escape hole in different places. Sooooooo.......... you need that carbine barrel that is specially made. In all honesty - you would be much better off to simply buy the complete assembled disapaitor upper. By the time you piecemeal it together it will cost you more.

You really should go invest in some reference materials before doing a build like this. I say this because the front sight tower and gas block - have nothing to do with the handles....... that is held in place by a simple front handguard holder that slips on before the gas block is put in place. You want a copy of the "Complete AR-15 Assembly Guide' that can be found at amazon.com and Barnes and Nobel. It shows you the pitfalls in different assembly points and the correct tools to use - and - tells you why you need them. Dropping $400 in upper receiver tools to save $90 in labor for a pre-assembled upper makes no sense............. not unless cracking and tossing upper parts several times a month is part of your shooting hobby.

You can easily drop the pins on the front sight tower of a pre-built upper and install a YHM flip up sight. The YHM ones bolt on with 4 hex bolts - this makes the install very simply and allows you to get an excellent alignment on the gas tube to the bolt. This will be 50x easier and less expensive than building.

EDIT:

I got your email - but - I cannot reply because your mail box is set up so nobody can contact you! LOL. Let me know when you have that issue resolved.

Your only real problem is that the hand-guard is retained by the rounded triangle stamping that's right behind the gas-block. You need that piece to hold the two parts of the guard together. There isn't enough room under a standard A2. Plus, the gas-block is a major source of heat. I don't know if the plastic could handle it even if you could find one the fit. From a functional perspective, you would probably be better off just building a standard "dissipator" with a railed gas-block, and leave off the front sight.. Have you looked at M1S? I think they sell a complete upper that's very close to what you have in mind. They are a budget shop, but they allow for a huge numbers of variations to their standard offerings. If nothing else, it would give you some ideas.

I am assuming you have found a dissipator barrel like one of these.

http://www.model1sales.com/index.cfm?fuseaction=ca...

You say mid length gas tube, but a 16" inch barrel should have a carbine length gas tube, mid length would be for an 18" barrel. There are barrels being sold that are simply shortened, with a rifle length gas tube, but you should avoid those because they will be finicky about ammo choice. I have experienced that myself.

The barrels at the link have an option for a low profile gas block with no front sight, but it would also be easy to replace the front sight base with a Picatinny rail mount for a front sight. You would have to fabricate a pin to substitute for the gas tube because normally the gas tube is what prevents the handguards from spinning around on the barrel.

See how this part provides a pin that holds the hand guard from turning? Your gas block will need something similar, like a large roll pin perhaps.

http://www.midwayusa.com/product/877023/doublestar...

There are uppers you can get that do not have a fixed front sight; you have to attach one via a rail. And they do make types that work with standard hand guards. It can be done but you need to get the right product.

Sure. I have a barrel stretcher that you can use to make everything fit. They really should require an IQ test before they sell tools to build an AR-15.

....( nice fantasy ) you're full of it. After looking at some of my answers, then you should realize just how many stoo-pid, repetitive and ridiculous questions are asked by all you "experts". If people are sooooo dumb that they even have to ask some of the ridiculous things they do on here, they deserve to get trashed...besides, stoo-pid people don't like being told they are stoo-pid.