Could be you've got lemons.
I have two, and like 'em better than the factory mags. As an added benefit, they have a real smooth finish that helps with the trigger pull. The magazine safety moves against the magazine during the trigger pull, and if the magazine has a rough surface, it adds "grit" to the trigger pull. I have one bad aftermarket mag (USA magazines? can't remember) that yields a really bad pull.
My KRDs give a nice pull.