I am considering a mounting a compact red dot on a G19, G34 or even a G21. So far I am looking at the Trijicon 4 MOA (~$420), C-more 3.5 MOA (~$330) and the JP 4 MOA (~$320). All have mounts for the dovetail on Glocks. Do I have more alternatives? Any one used NcStars? Have anyone used any red dot on your Glocks? What is your experience? Does it have to be re-sighted every time you replace battery? Will these take rapid fire? How much abuse will they take? Glass or plastic? My apologies if there is another thread on the subject but I was not able to find it.