This may sound like a dumb question.

[Team Helotes]

I am building up an Iron Ridge uppe DPMS style. I called and talked to Walther about a barrel. I was all set on a custom super heavy. They said a lighter barrel would be fine and they have some in stock. The stock ones use Armalite gas system. He said I would need a different gas tube than my standard AR tube. I looked online and found them.  My question is are the gasblocks the same?  I have built several ar15 but this is my first big gun.

[Jgun]

The Armalite gas system is slightly longer than the DPMS, around .250" I believe. This is why you will need a longer gas tube. The gas blocks should be interchangeable between the two platforms as long as the Id of your gas block matches the OD of the barrel in the gas port location, the common sizes will be .750', .875" for a lighter barrel, and .936" for a heavy barrel. Of more importance is that the bolt/BCG match the barrel extension. I have heard different from certain people, but most of us usually match the BCG to the barrel type, so if your going to use an Armalite barrel, to play it safe you ought to use an Armalite, or Amalite type BCG. If you've already got a different BCG, you might want to decide if you want to switch BCG's or would you prefer to get a barrel that matches the BCG you've got?

[Team Helotes]

I told Walther I had a DPMS carrier and the said they are also including a bolt for the barrel that will work with my carrier.

[Jgun]

Then you should be GTG. Is the barrel he's supplying, an Armalite brand barrel, or just an Armalite type? Have you already decided what you want to use for a gas block and hand guard?

[Team Helotes]

It is one of their barrels.  For the gasblock I will order a Troy, I have used them on 4 other builds and like them.  I have a 13.8" Troy Quad rail that tracking shows will be here tomorrow.