Step one. Remove bolt
Two: Insert your magazine with a round loaded.
3: Look down the arse end of your receiver. If you cannot see the edge of the primer pocket invading the receiver bore then you need more case overlap. This is why it runs like poo.
Couple ways to resolve this. You could molest the feed lips and it might help you some. The range to work in here is quite small. The edges of the lips need to be just under the tangent point(s) of the case body, otherwise they get grabby. You'll feel it immediately when running the bolt. You want flats on the case, not the edges.
Another way is to go black smith and sink the DBM into the stock more. Not the easiest thing to do at home and they have a habit of looking like total crap because now everything is sunk in the stock.
Yet another is to remove the release lever and modify it. If your a ninja with a TIG welder you can add a zip of material and shape it on a belt sander. -I've done this. Another way is to turn a pin from mild steel and press fit it into the release lever hole. Then relocate the hole lower so that it raises the lever further into the magazine well. I have done this as well. You can't go very far with this as the louver feature on the back of the mag hangs up where the clearance slot is on the back of the mag well at some point. That and the mag box lid hits the bottom of the DBM also. There is a narrow range where this does work however. Done it more than once for folks.
The key here is getting the case to present properly to the bolt face. The primer pocket/receiver bore should form an upside down figure "8" when its correct. You do get a narrow margin of error. Too low and your back to square one. Too high and feed lips start dragging on the bolt body. That'll really feel like crap if the bolt is fluted.
Hope this helps.
C.
