Right now, I need a gas key. Looking at DPMS, it seems they list the same part for AR-15 and .308. Can I use any AR carrier key/DPMS? So does that mean that you bought a stripped bolt carrier? The gas-key is sometimes already screwed and staked on the carrier. Just wondering. As far as the barrelnut for the forearm. The barrelnut screws down the barrel to the upper, then the forearm attaches to the barrelnut. But don't take this as gospel. Try "dry-fitting" stuff together and take a good look at it. Ron