You probably 'bowed" the sides of the mag outward when you removed it and have to squeeze them back together. Its best if you use a square on the rear and/or front ends of the mag to get the sides square otherwise it could be bowed, one side in, the other out end to end.
Don't trim the tabs! To reinstall them I set the rear tab in first then use a screwdriver in the corner of front tab at a 45 angle then thump it back and down.
Bill
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