1) Correct. Unscrew the screw, pull the extension down until the retaining tabs are cleared. There will be a large spring for the collapsible stock mechanism. It won't jump out with force.
2) The manual was written for the 556 with the AR stock. Apparently those came with the fold down sight. Here, it's a matter of choice whether you want to co-witness or not. Some will argue against, I have yet to form an opinion.
Theoretically though, at your preferred shooting distance and depending on your preferred sight picture when shooting iron (center mass v. 6 o'clock) the red dot will either be above the front post, or right on the tip.
3) In my case, on the 522 with the SIG diopter, I placed the red dot just in front of the diopter with the necessary clearance to allow me to put the protective cap back on.
4) Hard to know what you don't know, know what I mean?!
2) The manual was written for the 556 with the AR stock. Apparently those came with the fold down sight. Here, it's a matter of choice whether you want to co-witness or not. Some will argue against, I have yet to form an opinion.
Theoretically though, at your preferred shooting distance and depending on your preferred sight picture when shooting iron (center mass v. 6 o'clock) the red dot will either be above the front post, or right on the tip.
3) In my case, on the 522 with the SIG diopter, I placed the red dot just in front of the diopter with the necessary clearance to allow me to put the protective cap back on.
4) Hard to know what you don't know, know what I mean?!