10-4. QUESTION: Will an AR-15 (CAR) stock fit an AR-10?
ANSWER: Yes (with caveats). You will need to use either the carbine AR-15 carbine lower receiver extension (buffer tube) with an AR-10 spring and a shorter AR-10 buffer (to allow for the longer AR-10 bolt carrier group) or an AR-15 stock and the AR-10 buffer tube (but it will not collapse all the way). The A2 stocks are the same. The AR-10 rifle buffer is a little shorter in the AR-10 rifle.
http://www.armalite.com/Categories.a...f-fb5caf8043a3

If you go through the FAQs it might answer your other questions.

Hope this helps.