Post a photo but I think what you are seeing is correct. Right side has a small rib along the bottom whereas the left does not because of the large flare where you would normally expect the sling clip. That is normal, but post a photo as I have seen plenty of .40 clones where the receiver was not rolled evenly. Even with the a sense of the flare on the left, it should be even with the stop-rim on the mag.Anybody notice the mag wells on the MP5 40/10 have a flaired lip on one side (mates up to ridge on the mag) but not the other? How are they supposed to be? CAn this be fixed by smiths?
Well kick my but I just got an HK MP5 .40 magwell today for the release parts and Clicker's description is right on, the HK one has a rib on one side and flat on the other and it does look like the clone flats.I wouldn't call it flared more like a rib along the bottom right hand edge of the magwell. I suppose it's to strengthen the edge since the mag has a flange that acts as a stop against the edge of the well.
The left side lacks the rib but there is a stamped profile on most the left side of the magwell.
These features on my 10mm Coharie magwell look practically identical to the magwell of a German MP5/40 receiver section I have.