I have picked up quite a few DBM in the last month. I have a Badger, a Seekin precision, Hooper Ordnance and a Surgeon. All of these use the AI mags except for the Seekin. I have at least three of the badgers on different rifles and it is a good one. The Seekin has a push button to drop the mag and the Surgeon has a lever next to the trigger guard. Now the Badger does have a lever that sticks down and someone makes a lever that rides next to the trigger guard. I have one of those levers on one of my badgers.
I also have a HS Precision DBM. It is a good basic set-up in it's time, but you can find better ones. The 10 rounds for the HS are a little pricey compared to the AI mags.
I can tell you that you can not go wrong with any of the ones I have listed. Good luck.