I don't own one, but your DPMS takes SR25 pattern mags.
Rainier is a site sponsor, and the authority on 308 ARs. They have the drum for a few bucks less. http://www.rainierarms.com/?page=shop/detail&product_id=2953
Give them a call before you order, if you want to be absolutely sure. They were very helpful when I asked rail compatibility questions on my 308 build.
It should fit because the video on Rainier Arms demonstrates the drum with a MEGA MA-TEN. My MEGA MA-TEN works with Magpul Pmags which are DPMS pattern so it should work fine.
I was just thinking yesterday about a .308 drum or something. Now I know. Thanks.