If they (Mag Brakes) are like the full size 75 Brakes, they just have a "crease" across the flat spring main spring protector maybe 3/4" down below the top pin.
This "crease" is what prevents the mag from falling farther than just far enough to pull the mag out by hand.
Flatten the crease on an anvil; or buy a mag stainless brake without the crease (Drop Free brake), and your mags will drop free.