I've stirred up a bit of healthy discussion about the need for mag button clearance on carry holsters, and think it would be helpful for the need for it to be well understood.
Have I ever heard of anyone losing their mag from pressure on the mag button with the holster? Yes. Heard of any makers who were sued for this? Yes. Heard of any maker who lost their cases? Yes. Makers, don't let this be you, too.
Put it this way: if holster makers knew 100 years ago that the mag button had to be given full clearance to prevent accidents, don't you think YOUR contemporary maker should get it right?
Here's a cutaway of the old M1916 holster, and the leather-covered plug that's inside it. No, it's not a cocking shelf; its sole purpose is to stand the pistol mag button away from the holster:
Holster makers, and holster consumers, are out of excuses for not clearing the mag button. This is the 21st century, not the 1870s or even the 1970s.
And further, being able to pop a full mag out to check that it's topped up, or to change full or partial mags without unholstering, is why it's de rigeur for professionals, including competition shooters to have a cleared button.
P.S. the M1916 holster was/is never made in left hand and the issue of mag button clearance therefore never needed to be addressed for lefties.