The thing is, there are a few different kinds of DBM's.

1. "old style" that are stagger feed and have the release button in the side of the stock (Most stocks for these require bottom metal that isn't hardly available, it's long past production and few were ever made).
2. Center Feed long action (and short action) that have a plastic mag release on the mag itself ("Axis Style")
3. Center Feed long action (and short action) that have a metal, spring loaded release on the bottom metal frame or "surround".

To better advise you, I think it would be best if you could send us a pic of your action and your current mag setup so we know for certain what you have.