The Armalite AR-10 does in fact use a modified M-14 type magazine. The Armalite AR-10 magazine has a slot cut in the side of the magazine and I think a different follower but I am not sure about that. The cheapest route though is to probably just buy the AR-10 magazines from Armalite unless you already have several M-14 magazines. One of the problems with the 308 ARs is that the different manufacturers use different magazine designs in their rifles and ofttimes different part designs. What this means is that there is not the degree of interchangeability with the 308 as with the 223 so you need to be sure and stock magazines and parts from the manufacturer of your particular rifle because parts/magazines from a different manufacturer probably will not work. Since you said you are new to this, don't scrimp on magazines, this is the most common cause of functioning problems with semi-auto firearms and a lot of aggravation can be saved by using first rate magazines. Hope this helps
