Originally Posted By: WSMBUCKHere is what Armalite says.
GT-3. QUESTION: Can a DPMS/POF/KAC/RRA upper be put on an ArmaLite lower receiver?
ANSWER: You can install ArmaLite, Colt or high quality components made to military standards to ArmaLite M15 lower receivers, but ArmaLite doesn’t recommend it. We recommend that you use ArmaLite upper receivers for optimal fit, matching to the deep black color of your ArmaLite receiver, and the basic knowledge that your rifle isn’t totally mixed up.
Let me clear this up for you a little. Here is the whole quote you should have posted from the Armalite website. Make sure to read the last sentence of my quote. It seems to be the relevant part of the answer that would help answer the OP question.
GT-3. QUESTION: Can a DPMS/POF/KAC/RRA upper be put on an ArmaLite lower receiver?
ANSWER: You can install ArmaLite, Colt or high quality components made to military standards to ArmaLite M15 lower receivers, but ArmaLite doesn’t recommend it. We recommend that you use ArmaLite upper receivers for optimal fit, matching to the deep black color of your ArmaLite receiver, and the basic knowledge that your rifle isn’t totally mixed up.
No other brand of upper receiver fits the ArmaLite AR-10 family of rifles.