Howdy, all. I finished my 9mm SBR project for a while now but the build has been plagued with feeding and extraction issues every tine I've taken it to the range. I've held off posting here until I had tried enough magazines from different manufacturers to eliminate that as a possible culprit, but I think I'm admitting defeat and calling for the big guns in here for help.
First off, the build. RRA 7.5 9mm complete upper. DPMS lower with same LPK. RRA 9mm hammer and RRA 9mm buffer, tube, and spring. Hahn dedicated mag block. Promag and CProducts magazines.
The issues. With the Promag, I get failure to feeds. A single round is stripped from the magazine and is lodged diagonally between the bolt and the barrel. It's as if the case head doesn't caught by the extractor claw and then wedges itself between the bolt and barrel. With the CP, I get double feeds. Usually, the empty case is stacked on top of an unfired round. Some instances, the empty is stovepiped or even flipped backwards.
The other issues. Bolt hold open occurs randomly with both magazines. The percentage is higher with Promag but I've had it happen where it also doesn't lock back. If I manually apply force under the magazine with my hand and then cycle the action, the bolt does lock on both types.
To me, it seems like the mag block isn't high enough. Since it's the dedicated Hahn, I can't adjust its position in the mag well. I'm tempted to try a different mag block, but I'd like to hear from you guys first before I purchase another one. I don't want this to turn into a Hahn/RRA/DPMS bashfest because the quality of the components are good. I just think my combination of quality parts is skewed dimensionally somewhere and that's causing all my grief.