Here's the photo of a PTR-91 magazine release. The U.S. government, (BATFE) has infringed upon the law - dictating the removal of the original G3 paddle release next to the magazine, among other worse crimes.
However, as you can see, if your hand is at least 7.5" in length, you can reach the PTR-91 magazine release with your trigger finger, without releasing your grip. If your hand is shorter, then you are going to want a Tac-Latch
for quick magazine changes.
Make sure to thank your government
for breaking the law!