bc..... The last DBM I did was a Win. several years ago. I'm trying to remember if the whole mag. assy. came out or not. I guess what I want to tell you is I try to take all of the mag. assy. off the gun if I can. Does the metal box that the clip slides into not come off? In non-DBM's, I take out the mag. box and spring/follower. The cavity left in the stock is filled with clay about half full, making sure that it is even with the top of the cavity where the bottom of the action meets it.
After the epoxy has cured and you take it apart, it is a fairly easy job to remove what glass has accumulated ontop of the clay, and push the clay out. Same with trigger cavity. A Dremel Tool saves a lot of work both during the prep stages and the final dressing up. Just be "light-handed" with it. Hope this helped.......