There are different methods of zeroing your AR-15 depending on the sight type, barrel length, and perceived use.  This page offers several methods to choose from.  Most of these methods require use of a 25 meter (27.33 yards).  Most civilian ranges are in yards, if you cannot set the targets at 25 meters, then shoot at 25 yards.  At 25 yards the bullet should strike 3/8" below the point of aim to approximate a 25 meter zero. 

The zeros for the optics (Reflex & Aimpoint M68) are the ones that were/are used by the U.S. Military (per their manuals).  These zeroing procedures depend on the sight being roughly in line with the iron sights (or where they would be).  This means a flattop mounting or mounting the sight in front of the carry handle (through the use of the 'gooseneck' mount provided with the sight for such a purpose).  If you have previously zeroed your iron sights, then attach an optic, BE SURE TO REZERO YOUR IRON SIGHTS.  Adding a optic (epscially mounted to the carry handle) can change your zero.  When I added my Reflex to my A1 carry handle, it shifted my iron sight point of impact 5" low at 50 yards (the same occured with a Reflex 2 on an A2 carbine).

Also note that all these zeros assume your Height Over Bore for the sights is 2.6" (iron sight height), with the exception being the Reflex Zeroing procedure which assumes a HOB of 2.8".  If you are using a scope check the Height Over Bore before you use these zeros.  If the scope is mounted much (greater than a few tenths of an inch) different (high or low) than 2.6" then use a ballistic calculator (we have free software for both  PC/MS-DOS and PDAs - Palm OS in our Documents section) to compute a more appropriate zero for your rifle/optic combination. Also in our Documents section (under Test Results) is a Excel spreadsheet (Ammo Track.xls) that shows the trajectories of several zeros with M193/M855 with the M16A2 & M4, it includes comparative graphs.  You can view a low-res version of the zero comparison chart HERE.

Note: you could also use an online ballistic calculator if you have neither a PC nor a Palm compatible PDA: ( http://www.eskimo.com/~jbm/ballistics/traj/traj.html) or ( http://www.snipercountry.com/ballistics/index.html)

If you've never used aperture/ghost ring sights before the I suggest reading the Sights/Optics FAQ on Sight Alignment.

PDA indicates a PDA readable version is available in the File Cabinet for your use on the range.

Improved Battlesight Zero by LTC Chuck Santose.  A great all purpose zero for all rifles/carbines (no matter the iron sight type); and you zero in yards (50) instead of meters.  It keeps the bullet within 2" of the point of aim from 8M to 220M (very flat trajectory).  Also perfect for carbines with A1 sights; and ARs having a 'Red Dot' type sight inline with their iron sighs [on a flattop or in front of the carry handle]. PDA

50 Yard Zero (Comming Soon) Used by many carbine instructors this is a basic zero that can be used by all sight systems with a 2.6" HOB.  Kinda like a IBSZ simplified. 

New Marine 300 Meter Battlesight Zero Per MCRP 3-01A (and in D. Scott Griffin's Book).  Now the Marines are zeroing point of aim to point of impact at 36 yards (A2 rear sight should be set to 3).  This produces a proper 300M far zero.

Marine 300 Meter Battlesight Zero Per M16A2 Operator's Manual.  The official sighting in procedure previously used by the US Marines and currently used by the US Army.  If you set your rifle to the -3 clicks specified, it is supposed to give you zeros at 100, 200, 300 etc.. meters (but doesn't since this method has been proven to give an improper zero). PDA

Army 250 Meter Zero for the M16/M16A1 Rifle Per DoD sources. The official method of zeroing M16A1 rifles.  Only useful for rifles with A1 rear sights, and primarily those with 20" barrels (for carbines with A1 rear sights use the Improved Battlesight Zero).  Its big advantage is when shooting the 25M Schedule C Qualification Course.  Just flip to the L sight aperture, and you have a perfect 25M zero, flip back to the short range one and your rifle is 'battle' ready.  PDA

9mm AR-15 Carbine Zero by LTC Chuck Santose.  Looking for a good zero for that 9mm AR?  This zero is for a 16" carbine using 115gr 9mm (and the 147gr 9mm round).  Good for use with iron sights or a dot sight.

Reflex/Reflex 2 Advanced Combat Optical Gunsight Zero Per the manual. A 300 meter battlesight, with tips specific to the 12.8 MOA triangular reticule and the 6.5 MOA dot. PDA

M68 Close Combat Optic (Aimpoint) Zero Per DoD sources.  This is how the U.S. Military zeros the M68 Close Combat Optic (Aimpoint Comp M/XD red dot sight).  This is a 300M zero, and is set up to hit the same point as the iron sights (typically the Marine 300 meter zero). PDA

Zeroing Telescopic Sights with Built In Bullet Drop Compensators (BDC) Per our experiences on the range.  This is a method that allows one to easily zero their BDC type scope.  This works for those compensators that are mechanical (i.e. Colt, Leapers (Colt clone), Elcan) or those that have reticules with extra crosshairs for bullet drop compensation (i.e. Trijicon ACOG scope).

25 Yard Method of Zeroing  Per our experiences on the range during MD AR shoots.  During our AR shoots we needed a method of quickly and temporarily zeroing for 25 yards (to shoot the Alternate Course C Qualification).  It is not a recommended initial zeroing procedure, but it should be close enough till you can get to a 50 yard range and verify the Improved Battlsight Zero (the 8/3 - 2 setting).

 

Sight Adjustments at 25 Meters

Barrel Length	Sight Type	Adjustment @ 25M	Az/El
20 "	A1 Front (round)	1/4"	EL
20 "	A1 Rear	1/4"	AZ
20 "	A2 Front (square)	3/8"	EL
20 "	A2 Rear	1/8"	AZ
14.5" or 16"	A1 Front (round)	3/8"	EL
14.5" or 16"	A1 Rear	3/8"	AZ
14.5" or 16"	A2 Front (square)	1/2"	EL
14.5" or 16"	A2 Rear	3/16"	AZ
N/A	Reflex ACOG	7/32"  [1/4"]	EL
N/A	Reflex ACOG	7/32"  [1/4"]	AZ
N/A	M68 (Aimpoint)	5/32" [1/8"]	EL
N/A	M68 (Aimpoint)	5/32" [1/8"]	AZ

Note:  For those who use the Metric System (5/32" = 4mm or 1" = 25.4mm).

Measurements in brackets [] are a close approximation.