So is this guy mistaken?Originally Posted by lysander
https://www.youtube.com/watch?v=wzINqoSP4Eo
|
||||||||||||||||||||||||||||||||||||||
Member
So is this guy mistaken?
https://www.youtube.com/watch?v=wzINqoSP4Eo
Senior Member
1) If you are going to zero any of the M16A2 style rear sights per the Army FM, you do not mess with the elevation setscrew, period. You just leave the rear sight the way it came from the factory, which should have 8/3 or 6/3, 3-clicks up from all the way down and if it isn't, it doesn't matter. In fact, the Army's FM 3-22.9 - Rifle Marksmanship M16/M4 Series Weapons, never even mentions the fact that the elevation knob and elevation index are separate and the setscrew even exists. Even the USMC manual notes that messing with the setscrew is an armorer's function. So, as far as the military's concerned, the elevation knob and index are a solid mass that never moves.
2) If zero an M16A2 per the FM (with a 25 meter reduced size zero target), you get a pseudo-300 meter zero, based on a lot of assumptions about the trajectory and the sight. How the Army wrote the manual and how the sight was intended to work are two different things, even though they both get you to the same place. The USMC manual has zeroing taking place at a 300 meter KDR, or at 36 yards as an expedient.
3) I didn't hear the guy reference the M16A2 versus the carry handle rear sight so I can't say.
Member
The guy shows a carry handle sight with the 6/3 drum and refers to it as an "A2 rear sight."
Senior Member
An M16A2 rear sight elevation index makes one revolution and goes from 300 to 800 meters in 25 clicks.
The carry handle rear sight elevation index makes one revolution and goes from 300 to 600 meters in 24 clicks.
Member
Upon rereading this thread, I noticed that this illustration provides a possible explanation for another problem with my carry handle sights. I've got three identical sights, but they vary in the number of total clicks available. From the bottom position I make one full revolution of the drum and then count the extra clicks I have available before I top out. Sight number one gives me three extra clicks; sight number two, five; and sight number three, eight. If I wanted to set up a RIBZ--which requires six extra clicks below the 300 meter setting--sight number three would be the only one I could do it with and still be able to go all the way up to the 600 meter setting.
The illustration shows a vertically-oriented slot cut through the lower portion of the threaded part of the rear sight base, a roll pin inserted through the slot to keep the enclosed spring in place. It would appear, then, that the total number of clicks would depend on the length of the slot, slight variations in the milling of the slots possibly accounting for the variations in the total number of clicks.
Thoughts?
Member
That makes sense to me. Seems the main cross pin captures the sight base, the spring keeps tension, and the slot you mention is what allows vertical movement, while allowing no appreciable rotational movement (just that little wiggle present on A2/A3 sight bases).
You have located the discrepancies, it would seem 👍
Last edited by 498cm3; 03-14-23 at 15:47.
Member
I'm now mulling over possible remedies. What about having the slot milled all the way out through the bottom and then welding or epoxying a small, thin washer across the bottom that would butt up against the roll pin when the adjustment tops out?
Member
I wouldn't cut it all the way. A little adjustment would probably go a good ways. A small round needle file would do it.
Last edited by 498cm3; 03-14-23 at 21:59.
Posting Permissions
Reply With Quote
Bookmarks