Hello, when I attempted to install a NM rear sight on my Colt AR, I damaged the large spring that is inserted into the threaded post of the rear sight.  The damage occured when I drove the rear sight pin back in and it hit the spring. So now I have a few questions:

1.  When I replace the spring with a new one, how do I drive the pin back in without doing any damage to the spring?  

2.  Since the pin has to pass through the spring in order to be driven in, should I use the rear elevation knob to push the sight all the way down or leave it up, or in the middle before I drive in the pin?  (I think I should leave it all the way up in order to maximize the vertical separation between the spring coils and allow more room for the pin to pass)

3.  What would happen if I install the rear sight without this spring?  The rifle that I took it off of, did not have the spring inside the sight post, so I think that the previous owner had the same installation problem and just skipped the spring (probably after mangling it like I just did).

About the simplest way to install any A2 sight is to engage the threads, rotate the elevation knob down completely, then come up with the elevation knob.   The -23 calls for 22 clicks up on a standard A2... You may have to eyeball your NM to be sure you're aligned with the spring pin holes.

Install the helical spring, start the spring pin but don't go through the receiver completely, compress the spring with a dowel or small screwdriver and tap the spring pin in until it's over the spring, compress the opposite side and finish installing the pin.  

The pin passes over the spring, not through the coils...

[url]www.ar15.com/content/books/TM9-1005-319-23.pdf[/url]

Right click the link and select 'save target as' to download the -23 Unit And Direct Support Maintenance Manual to your computer...