It's not that the barrel nut is larger than the ar15 is a misconception! The threads of the nut are a larger diameter and pitch ( armalite and dpms are same diameter, but different pitch). I've changed handguards between 10 and 15 and as long as the same manufacturer was used the guard fit both. Not all will do that though. As far as compatibility goes check for the shape of the upper and lower receiver near the buffer tube. Most dpms will have a rounded ( like ar15s do) where the upper and lower contact above the safety. Armalite has more of a 45 degree cut. With that being said Matrix Arms that I have has the armalite cut, but are dpms compatible. Another thing is the take down and pivot pins can be different length/diameter and are usually bigger/longer in the ar10s. Most triggers work in both as long as the trigger pins that fit the receiver are the same size as the trigger and hammer hole size. Buffer tubes (except armalite are interchangeable. Buffers (length of) usually are not. Buttstock fitment (commercial or mil-spec) for best fit only fit like specs.