Well, I took the 556 out for a spin today to sight in the new Sig diopter sights.
Long story short- There is insufficient elevation adjustment on the rear sight. It tops out at approx 6" too low.
While it is possible to raise it up a little bit more, at that point it has darn near come unscrewed, and the drum just wobbles around. It would appear that there is hope of making it work, but it will require taking it apart, which I have been unsuccessful at doing for the last few hours. Not to mention being sure to void the warranty... Shimming the rear sight is a no-go, as it is quite a precise fit with the rail, and would succeed only in deforming the locking plate when it is tightened down. Am sure not going to file down the front sight, either.
The thing is very far from mechanical zero; as is the front sight. The latter required to be almost all the way to the left with the rear sight centered.
![]()
![]()
^ These are the elevation "stops" v
![]()
Another area of interest:
![]()
I think that this will be just fine after I file the stops just a smidgen. MIght be a good idea to open up the windage detent elipse a little bit, also.
ETA>
At any rate.. SUCCESS!
After breaking the rear sight down, and very closely examining all the different surfaces that come into play during elevation adjustments, it became obvious that the culprit was that almost non-existant eliptical cutout for the windage detent. This significantly limited the available elevation adjustment. A few minutes with a round file, and the available adjustment area about doubled. [
]
Cleaned it all real well, and greased it up. As measured on my calipers, the 100m aperature now will adjust upward slightly past 1.0" (as measured from the bottom of the sight assembly), which is quite sufficient.
Long story short- There is insufficient elevation adjustment on the rear sight. It tops out at approx 6" too low.
While it is possible to raise it up a little bit more, at that point it has darn near come unscrewed, and the drum just wobbles around. It would appear that there is hope of making it work, but it will require taking it apart, which I have been unsuccessful at doing for the last few hours. Not to mention being sure to void the warranty... Shimming the rear sight is a no-go, as it is quite a precise fit with the rail, and would succeed only in deforming the locking plate when it is tightened down. Am sure not going to file down the front sight, either.
The thing is very far from mechanical zero; as is the front sight. The latter required to be almost all the way to the left with the rear sight centered.
^ These are the elevation "stops" v
Another area of interest:
I think that this will be just fine after I file the stops just a smidgen. MIght be a good idea to open up the windage detent elipse a little bit, also.
ETA>
At any rate.. SUCCESS!
After breaking the rear sight down, and very closely examining all the different surfaces that come into play during elevation adjustments, it became obvious that the culprit was that almost non-existant eliptical cutout for the windage detent. This significantly limited the available elevation adjustment. A few minutes with a round file, and the available adjustment area about doubled. [
]Cleaned it all real well, and greased it up. As measured on my calipers, the 100m aperature now will adjust upward slightly past 1.0" (as measured from the bottom of the sight assembly), which is quite sufficient.
