Quoted: Pay attention......Randall Rausch was bored and put a LR-308 extension onto an AR-10 barrel. It fits. You want a chrome lined barrel for the LR-308...just order an AR-10 barrel with the appropriate gas port location. Simon

"Appropriate gas port location" is the operating part of this sentence.
I don't have any factory DPMS barrels to measure for gas port location to compare to the Armalite barrels.
I don't know if they are exactly compatible.
If someone with a DPMS can take some measurements, from the rear face of the barrel extension to the rear face of the front sight/gas block, this would be very helpful for comparison purposes.
The rear face of the barrel extension is also the front inside face of the upper reciever so it's a very easy measurement, no dissassembly required beyond 2 takedown pins.
I would like the carbine and rifle lengths.

Quoted: Took these quick.  DPMS LR-308 24".  Hope it helps.

This is exactly what I needed.
I'll take those dimensions and drop them into my AR-10 AutoCad model and see how they compare to Armalite dimensions.
Thanks.

Quoted: This is exactly what I needed. I'll take those dimensions and drop them into my AR-10 AutoCad model and see how they compare to Armalite dimensions. Thanks.

Ok, I dropped those dimensions into AutoCad and here is what I found...

The rifle-length DPMS barrel is setup to use a regular AR-15 rifle-length gas tube.
Armalite rifle-length barrels use a 3/16" longer rifle gas tube.
When I drew my AR-10 barrel profiles, I designed around commonly available AR-15 rifle gas tubes and my drawing exactly matches the DPMS rifle barrel in the picture above.

Now for the carbine barrel...
Using typical AR-15 carbine length gas tube dimensions, the DPMS carbine barrel dimensions are within about 1/32" of my autocad dimensioned drawing based on known gas tube lengths.
I think this can be attributed to the tape measure being pushed against the gas block instead of stretched against the end of the barrel.
It's certainly well within where you need to be.

I have my own drawings of how I build mid-length, rifle and extended rifle length gas system AR-10 barrels.
I also have measurements from Armalite rifle-length barrels and Now I have added the DPMS equivalents to my drawing.
The only dimension I am missing is measurements from an Armalite carbine or mid-length gas system barrel.
Anyone care to contribute?
Hiredgunr's rifle picture shows exactly the measurement I need.

Now, as for barrel interchangability, it looks like you could use an Armalite barrel on a DPMS LR308 as long as you use the special rifle-length AR-10 gas tube along with the barrel.
Putting a DPMS rifle length barrel on an Armalite AR-10, you would use a typical AR-15 rifle-length gas tube.
With freefloating handguard systems, there may or may not be enough room for a DPMS barrel on an Armalite upper.
With the Armalite barrel on a DPMS, you can expect an additional 3/16" gap behind the gas block to the handguard.
Differences in Armalite and DPMS delta rings preclude you from using regular 2 piece handguards with an Armalite barrel on a DPMS receiver so a freefloat system is the only way to go.