I currently have a stock DPMS AP4 in .308.  I like the way it shoots, but I think I want something different with the upper.  Since I am looking at this to be a heavy metal 3 gun rifle, I think I want to extend my sight radius a bit, and the dissipator thread got me to thinking.   I have never had an AR upper apart, so I am trying to be cautious and not F anything up.  it looks like I would have to cut off the front sight, unscrew the forend, attach either a 9" or 12" forend and either clamp a new FSB out at the end of the bbl [or onto the end of the 12" rail]?   It seems simple when I just type it out like that.  

On the other hand, is it possible I could end up $$ or aggravation ahead if I sold the AP4 upper and just bought an upper configured the way I want?   Who sells DPMS pattern .308 uppers in a dissipator configuration?  Any guidance is apprciated.

I did almost EXACTLY the same thing to my AP4 a few months ago. I shaved down the original FSB (remove it first - its easier to work with), replaced the original carbine-length FF tube with a rifle length tube, and then replaced the original flash hider with a Miculek muzzle brake. In my case, I decided to mount an optic I had laying around to compete in HM Scope division, but a clamp-on front sight just behind the muzzle brake would work just as well (you could keep your DPMS rear sight of course).

The modifications went pretty smoothly - everything just threads together without the need for specialty tools. The FF handguard is a 2-piece design, so you can replace the short tube without removing the barrel nut from the upper receiver (though you do need to apply a good amount of heat and a couple of strap wrenches to free-up the Loctite applied by DPMS). Oh, and I also changed the pistol grip (totally optional of course) and found that a standard AR15 grip is an imperfect fit - the safety plunger spring hole needs to be modified, and there is still a slight gap above/behind the grip when installed.

Once I was done with the rebuild, I wrapped the FF tube with paracord (to keep it cool) and then I sold all the unwanted stuff on the EE. Overall, I'm pretty happy with the result, and the cost was modest once I sold off all the unwanted parts.

Here is a picture:

Love that look.
BTW how did u fasten the cord to the tube?
Micko

That's a damn fine looking rifle.  I had almost the same problem fitting an ERGO grip to mine, but I decided the little gap was just some extra cushion for the .308.

The only thing I wouldn't like is that the DPMS forearm seems heavy as heck for a freefloat that doesent even have any rails.  I guess it helps with recoil but damn.

I wonder if a PRI handguard would thread right on, too?
http://www.midwayusa.com/viewProduct/default.aspx?productNumber=753509

How to paracord wrap your FF tube:

1) Obtain para cord of your chosen color. I recommend "real" 550 parachute cord, with white strands inside a colored outer sheath, rather than the braided stuff you get at WalMart.
2) Cut the para cord to length. For a plain-vanilla aluminum AR15 FF tube, you will need about 4 feet of para cord for every inch of tube you want to cover - I found I needed more for the wider LR-308 FF tube (about 50ft total IIRC). Once cut, heat-seal the ends using a lighter flame to prevent fraying.
3) Cut another length of para cord to approximately 18" long, fold in half, and then tie a knot with the loose ends to create a loop about 9" long.
4) Soak the longer length of para cord (from step 2) in water until its saturated, then shake off the excess water. This is an important step, as it makes the para cord stretch slightly.
5) Starting with one cut end of the wet para cord several inches in towards the middle of the FF tube, lay the para cord lengthwise along the tube towards the end you want to start wrapping. Now start wrapping the paracord around the tube, keeping things as tight as you can and working your way towards the opposite end. The wrapping will cover the first several inches you had initially layed lengthwise, thus preventing it from unravelling. Keep an eye on things to make sure the cord lays parallel and no big gaps/distortions develop.
6) When you get within about 5" of the end, lay the 9" long loop of paracord lengthwise on the FF tube (knot towards the center of the FF tube), then continue wrapping the para cord so as to cover this loop. This loop needs to protrude about 2" at each end.
7) When you get to the end of the FF tube, insert the loose end of paracord through the protruding loop, and then pull on the opposite end of the loop so that the loose end of para cord is pulled under the wrapping and out where the loop is protruding.
8) Cut off any remaining loose ends of para cord, and heat seal as flush as you can with the wrapped surface.

I hope the above is clear. Once the para cord dries, it will tighten down nicely and prevent the wrapping from unraveling. I have wrapped several rifle FF tubes this way, and the wrapping has lasted indefinitely... never had one unravel despite years of hard competitive use in the AZ heat. Of all the FF tubes I have ever handled, my paracord wrapping is by far the coolest to hold.

The DPMS tube did not seem excessively heavy to me - all you are adding is the extra length. They offer a vented unit for a bit more $$$ if that helps. As you say, any extra weight does dampen recoil.

I'd transform it. You'll have more fun and you'll appreciate it more. You may even save a few bucks...

Thanks
StealthyBlagga

I absolutely do not mind my thread being used as a how-to, but would you mind posting pix for those of us that aren't good a t following directions?

Your Wish = My Command. I am the KING of MS Paint

I'll be damned, *thats* how you meant that...  I am gladd I did ask for pix, I would have fucked that up beyond the normal range of fucktupedness..

Damn, I am going to have to try that now.

Back on topic, tho, is the DPMS FFtube a standard thread?  Meaning, I assume any of the DPMS FF tubes will fit, but what about different brands?

The LR-308 FF tube is different from an AR15 FF tube - it is a lot bigger diameter. However, if you just want to replace the current LR-308 "carbine" tube with an LR-308 "rifle" tube like I did, then the threads will be the same. I can't comment on other aftermarket tubes/handguards though.