As stated before I'm not an AR guy but my understanding is that the hole is milled a little larger than normal and there's no spring. I have read that some guys have put other safeties in and that has helped. I did a couple drop tests when I got mine and it works as intended. It's actually harder than any other safety I have to actuate.
Interesting....
http://www.ruger.com/micros/rpr/models.html