1. Current Army/Marine Corps battlesight zero and it's procedures are well described in TM9-1005-319-10, the M16/M4 operator's manual. A recent copy of this manual is available for download at the Manual Depot. Procedures in the manual will not be repeated here. 2. The current 300 meter battlesight zero is a function of the sights on the rifle and I personally find it shoots too high for the vast majority of combat targets, including the Army's qualification ranges. The procedure listed here takes better advantage of the flat trajectory of these rifles as well as the use of civilian ranges, which are seldom surveyed in meters.
3. When zeroed at 200 meters, a distance twice that of normal combat engagements, these rifles have a very flat trajectory that is less then 2" from line of sight at all intermediate distances; a distance that's smaller than the normal dispersion of arsenal or factory loaded ammunition. This tiny trajectory arc allows very precise shooting out to 250 meters where the bullet is only 2" below line of sight.
4. A 200 meter zero has the happy coincidence of an initial trajectory cross-over at 50 yards, a distance available on almost all civilian ranges including many indoor ranges. This makes it easy to achieve a 200 meter battlesight zero without recourse to surveying your own range. If 200 meters is available you can fine-tune the zero at the real distance. And should when you get the chance.
5. The lowest sight setting, however, on these sights is 300 meters so the sight needs to be modified to preserve the markings on the sight (despite the fact that no one ever sets a range on these in the real world other than a USMC range). The sight needs to be set to bottom out at 8/3 -2 clicks. This will be the new 200-meter setting.
1. Flip the rear sight back to the unmarked aperture. This will reveal a hole in the top of the handle.
2. Rotate the sight wheel all the way down. Will probably be exactly at 8/3 (6/3). Don't force it down.
...
Click for Full Text!
Poster Comment:
Pics and instructions at link. Very informative site, but not updated any longer it seems. This is an easy mod. If I can do it, so can you if you choose to.