Straightening the Rear Sight on the M-16/AR-15
Service rifle shooters are a funny group. Some of them are annoyed by the "crooked" rear sight found on most stock AR's.
This is a match rear sight found on a typical "Service Rifle" The sight is held in this position by a spring loaded ball located in the front face of the sight carrier, in the upper edge in the picture. By placing a shim on the opposite face, the sight may be straightened.
The sight in the upper picture has been fitted with a shim, the thin vertical white line just to the right of the knob.
For those of you with sharp eyes, the above pic also shows a hooded rear aperture on the flip-over.
With the sight on the rifle a number of feeler gauges are tried, until the sight is forced straight. The required feeler thickness is noted, and a gauge about 0.003 thinner is selected.
The rear carrier is removed, the Parkerizing removed on the face opposite the tensioning ball hole (the hole near the center of the upper-right vise jaw). Using any solder you may have, a propane torch, and any of the Ruby, pink, red or Rose liquid fluxes, carefully "tin" the edge of the sight. Do the same to the end of the selected feeler gauge.
The sight has been rotated in this picture to confuse you. The tinned feeler gauge has been pressed against the heated and tinned area of the sight.
Now rotated again, the feeler gauge has been trimmed, first with a Dremel tool and finally with a fine file. The flux is cleaned and the sight is re-assembled.