Need adjusting to fit the panzer arms ar12 - ProMag Eksen MKA 1919 12ga 10 Round Shotgun Magazine

This was the magazine the internet said would fit the Panzer Arms Ar12, but the fit is so tight, it was a struggle to get it out. I use a micrometer which showed the back side of the magazine [metal section only) to be roughly 1/32 wider than the front edge. I used a hammer and lightly tapped along back edges unless it would slide smoothly in and out with no restrictions. I would have given it a 5 star rating if it would have came like this, but it wasn't exactly manufactured for this particular shotgun. Now it works perfectly.