Does the 20" barrel take the standard AR-15/DPMS rifle length gas tube or the Armalite rifle length gas tube? — 3 Answers

Use the Armalite rifle length gas tube. not too sure how Faxon can be wrong in their own barrel but they managed to do it. The standard DPMS version is too short as the previous user said. I usually really like Faxon but come on. You definitely need the Armalite version for it to be correct.

I purchased this barrel and have a DPMS pattern AERO M5. I have found that the standard rifle length tube is too short and does not sit close enough to the gas key. I had to return my standard size rifle length gas tube because there was a large gap and it was not long enough. This was determined after constant short stroking and measuring of the tube. After viewing the tube inside of the upper receiver, it visually was also short on the cam pin cutout. Armalite length fit perfectly.