Colt Front Sight Post Primer

Colt currently offers four different front sight posts for use on their AR-15 family of rifles and carbines.  The front sight posts can be categorized according to their basic shape, (square or round) their profile, (straight or tapered) and their height, (short or tall.)  The height of the posts are measured from the top of the sight post down to the top of the “flange” of the sight post.

The sight post with the part number SP64507 has a short, square and straight configuration.  This post has a nominal height of 0.270”

SP64507



Part number SP64665 also has a short and square post, but differs from the above sight post in that it has a tapered shape to it; broader at the base and narrowing at the top.  All of the Colt square sight posts have a nominal diameter of approximately 0.070”.  The height of this post is also 0.270”.

SP64665



Shown below are the square, short/straight and short/tapered sight posts side by side for comparison.



The sight post associated with the M16/M16A1 series of rifles has a round shape and is also short and tapered.  The part number for this post is SP61706.  It is slightly shorter than the two posts described above with a height of 0.260”.

SP61706



The last sight post is Colt’s tall sight post which has a nominal height of 0.300”.  It has a square and straight configuration.  Its part number is SP62447.

SP62447



Here is a pic with the round sight post and the tall sight post side by side for comparison.




The original round sight post has five equally spaced notches around the sight post flange for elevation adjustment.  Each notch corresponds to 1 MOA of elevation (when used with a rifle length sight radius).  The other three sight posts all have four elevation notches on their flanges corresponding to 1.25 MOA of evlevation.

To clarify which post is used when:

SP62446 - 9mm
SP64507 - (Non-Tapered) Rifle
SP64665 - (Tapered) Carbine
SP61706 - (Round, 5 Position) A1

I am not certain the width of the rifle and carbine sight post is the same at the top or should be. It was my understanding the carbine sight post was narrower due to the shorter sight radius thus covering the same amount of the target at a given distance.  Please clarify if I am wrong. I believe the carbine sight post is also dimpled on the bottom to make identification easier.

Great photos....

I've measured quite a few with  digital calipers and the square shaped posts are all the same nominal width at the tip.  Also the the tall post (SP62446) is not limited to the 9mm carbine, is is found on 5.56 models as well.

I measured 10 of each myself.

The rifle sight posts were .070+-.001

The carbine sight posts were .065+-.001

All of my samples were from Colt. I sent out an e-mail to someone I think is in the know to get a third opinion.

Great thread in any event.