A few questions have come up as to how exactly the Dueck Defense RBU is installed and how it works. I am not going to uninstall the RBU and then re-install it, but I will explain how to install it. If I decide to remove it from the G19L, then I'll make a full video of the install. It is not difficult to do and can be done at home with hand tools. This is the process which was used to install the RBU on my Glock.
You'll need a mallet with a plastic end, a punch and a metal file to do it right, though you don't really need the metal file, it'll just make the install easy. A good gun tool kit would work well (you could piece this stuff together from Home Depot or the like).
Refer to XS Sight's video of how to remove and install rear sights, it is essentially the same process, fast forward to about 4:10 -
You are going to take the RBU and remove the screws on the bottom, the screws that are in the sight dove tail. Clean those screws up as well as the channel, make sure its dry.
Take some blue loctite, just a dab on each screw, and eye gauge the mount to the center of the slide with a mallet, tighten the screws to hand tight. (No RMR install yet) Hit the range and see how the iron sights group at 7 yards. Loosen up the screws, tap with a mallet or push with your thumbs just a smidgen to correct zero.
If you are skeptical, have someone else shoot the gun using the RBU iron sights and see what happens, if you both get the same result, awesome, if not adjust as needed. After you get a good zero, give the screws a quarter turn each, you can dab another very tiny bit of blue loctite on each screw if needed, otherwise you should be ready for the next step.
Do not use the RMR screws that came with your RMR, they will not work properly. Remove the screws from the RBU, clean the whole bit up and make sure its dry. Make sure you have a new battery, install the RMR and hand tight the screws, same as the screws above, quarter turn.
(above is from a range report)
Hit the range and zero the RMR to whatever distance you want. I suggest 25 yards, so you get a cowitness between the two sighting systems.
The entire system needs to mate together and the whole thing may walk so after about 100-300 rounds you need to confirm the zero at 25 yards (or whatever you made it at). After that you shouldn't have any more issues.
So far I have no issues with the mount, no issues with the zero walking after a zero confirmation after 250 or so rounds. I have not carried yet just yet but when I do I will report back with my experiences.