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How to Zero your AR15 / M4 / M16A2 Platform: Mechanical Zero & the 25m Target

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How to Zero you AR15 / M4 Platform: Mechanical Zero & the 25m Target

I have gotten a lot of requests from new shooters who have purchased an AR platform and are wondering how to sight it in, I explain the process that I learned while I was in the Army.

How accurate this procedure? Well the only way to prove this is by splitting playing cards which I have done from 20 feet out to 300 feet away (even left & right handed). The proof is in the pudding.

There are many different types of sights & even different zeroing procedures & targets & procedures, so keep in mind this is NOT an all inclusive class but it will give the basic steps on how to set your AR rig for a condition called “Mechanical Zero” and explain how to use the M16A2 25m Zero target I learned in the U.S. Army. The 25m Zero Target allows the shooter to ‘zero’ in the sights for that individual shooter so they can effectively engage targets at 300m (and longer). Here is a link to a pdf file of the 25m target you can download…

All information is for education/informational purposes only.

I hope you enjoy this vid and learn how to zero your AR platform.

😀

Steve

P.S. Do NOT get hung up on using an M4 25m target or the M16 25m target – they are basically the same but one the boxes or grids are slightly bigger. Heck I have used hand drawn grid paper to zero & it worked fine. Fact remains you still ‘walk’ your groups in by firing 3 rounds, adjusting your sights & fire again as needed till you get 3 out of 5 rounds in the circle (verify again to make sure).

P.P.S. Also do NOT get wrapped around the axel about the difference in peep sights. The larger aperture is for low light conditions, NBC mask & night vision use. The smaller is normally used for day time. Normally to zero you should use the small but you can zero using the larger one. What is most important is using the correct marksmanship fundamentals = grip, stance/position, breathing, sight alignment/sight picture, trigger pull and follow through. If your consistent then you can shoot with great results. I know some old army buddies that hit targets 250m+ without a front sight post or a rear sight apertures. Some ppl prefer using one over the other but whats important is putting the rounds on target. If you use the small peep or the large & get the job done, then great. However do NOT make this a point of contention, argue on this or other minor details – use what works for you and move on.

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48 COMMENTS

  2. You never zero with the large aperture. Ever. It’s made for low light shooting. You will be at the range all day if you try to zero that way. Small aperture only. Not sure how that wasn’t corrected for this video.

  3. 8:44. I dont understand this part. dont you have to adjust it up and left instead? so your sight is aiming at where the bullets are impacting? In the video, we are moving it right and then down. wouldnt it push the sight even further from the center?

  4. I’m new to AR rifles having only shot M1 and M14 in NRA high power, if anyone can assist, please reply. I purchased an A2, full USGI specs, (except for semi auto only obviously). The front sight has an “F” in the casting and the front post base was flush with front sight housing. Using M193 ammo. My rear sights have 8/3 on the wheel. I centered my windage, and came up 1 click to the “z”. My rounds are perfect left and right, but at the bottom of the paper. I lowered my front sight post all the way I could and the best I can get is at the base of the black image. Almost every time I fire a 3 shot cluster they are touching each other but low. I know I can come up clicks on my rear sight but isn’t the A2 supposed to zero with the small aperture on z at 300 yards? One final point, I am not “dotting the i”, I am holding the front sight bisecting the bull.

  8. The author is short on this subject. Here's how to do it from a re-write and edit of Military instruction: 
    Adjusting the rifle’s sights so bullets hit the aiming point at a given distance, the rifle is said to be zeroed.  The literal definition is when the line of sight and bullet path intersect and the resulting value in any form of measurement is zero. Properly adjusting the M4/M16-A4’s sights for a 300-meter Battle Sight Zero (BSZ) will sync the sights for a Bullet Drop Compensation function (BDC)

    The “Battle Sight Zero” supports engagement of unknown distance targets, allowing the shooter to aim center mass on an “E” type target and achieve a hit from muzzle to 300 meters with bullet impacting no more than 10 inches above point of aim, and hit to 350 meters with bullet impacting no more than 10 inches below point of aim. Utilizing the whole 20 inches of target below center of mass hold allows the shooter to hit a target out to 400 meters.

    Once zeroed for a 300-meter battle sight zero, the elevation wheel can now be hastily re-adjusted for engagement of known distance targets beyond 300 meters. This adjustment is known as Bullet Drop Compensation. The numbers on the wheel represent distances in meters. Bottoming out the wheel to 6/3 the BDC is set for 300 meters. Clicking up to 4, or 5 adjusts the trajectory of the round to engage targets at the corresponding distance (i.e. 4=400m, 5=500m). One full revolution up from 300 correlates to the number 6 on the left side of the 3. Thus set, elevation is now adjusted for 600 meters.
    Begin zeroing by clicking front sight post to where its base is flush with the deck of the front sight base. Next, set the small rear sight aperture, also known as the “daylight” aperture, in the up position (the larger aperture is only used when visibility is limited, shooting inside 200meters); and, turn rear sight windage knob to align index line located on the top of the large aperture’s outside rim with center index line located on the back of the rear sight’s base. Next, turn the rear sight elevation wheel counter clock-wise to bottom it out and then click it clock-wise to index the wheel’s 6/3 marking to the index line located on the left side of the carry handle above the elevation wheel.
    Now, because the path of the bullet will intersect line of sight twice when zeroing to any finite distance, this is how it is possible to sight-in the M16-A4 for a300 meter zero at 32 meters, or the M4 at 25 meters.  If precluded to a 25-meter range when sighting-in the M16-A4, you can compensate for the 32-meter to 25-meter offset by setting the M16-A4’s BDC 2 clicks clock-wise beyond the 6/3 setting, which will place the BDC wheel at the “Z” marking.
     So, using a target big enough to consistently understand the sight/target relationship, set target at 25 meters from firing point (27.340 yards), and from a stable position, using a center of mass hold, shoot 5 rounds to produce a group on the target. Triangulate the group,
    excluding bad shots, to define the group’s center point; and, adjust sights to
    move next grouping to target’s center.  Adjust elevation from front sight by turning
    sight post in counter clock-wise direction to move bullet point of impact down.
    Turn post in clock-wise direction to move bullet point of impact up. One click
    of post will move M16-A4 bullet point of impact 1.25 MOA, or M4 bullet point of
    impact 1.75 MOA. Adjust windage by turning windage knob clock-wise to move
    bullet point of impact right. Turn knob counter clock-wise to move bullet point
    of impact left.   One click of knob will move M16-A4 bullet point of impact .50 MOA, or M4 bullet point of impact .75 MOA.
    What’s an MOA?  MOA means minute of angle, an angular unit of measurement.  This unit of measurement, which is equal to approximately 1 inch per hundred yards, is used to describe
    the distance in inches a sight adjustment will make at target distance. For example, a 1 MOA sight adjustment would move bullet impact 1 inch at one hundred yards, 2 inches at two hundred yards, 3 inches at three hundred yards, and 10 inches all the way out to one thousand yards.
    Understanding the effect of sight movement in MOA is important to correctly adjust sights for
    bullets to hit where aimed; yet, the arithmetic for an understanding is easy. Using the simple math as shown, you can determine up/down sight adjustment needed; and, doing the math again, you can determine left/right sight adjustment needed.
    1.      
    First, think what the value of 1 MOA is at target distance:                                         
     Distance to Target in Meters / 100 = Value of 1 MOA in Inches at Target Distance
    2.      
    Next, think how many of those MOAS will fit into inches of needed movement:                                                                                                                                
    Inches of Movement Needed / Value of 1 MOA in Inches at Target Distance = MOA Adjustment
    3.      
    Finally, determine how many clicks to sight for needed movement:                                                                
    MOA Adjustment / Sight MOA Click Value = Clicks to Sight for Needed Movement

    For example, let’s say you’ve set your target out to 25 meters and you’ve produced
    a group which is 2 inches low and 2 inches right of the target’s center, with
    shots fired from an M16- A4. Remembering the front sight has a 1 .25 MOA click
    value, and the rear sight windage drum has a .50 MOA click value you can now
    determine sight adjustment needed:
    First, determine adjustment needed to front sight controlling up/down movement:
    1.       25 Meters
    / 100 = .25 Inches
    2.       2 Inches /
    .25 = 8 MOA
    3.       8 / 1.25 =
    6.4 clicks (round to 6 clicks) to sight elevation knob in clock-wise direction
    for needed vertical movement of grouping on target 
    Now, repeat steps to determine adjustment needed to rear sight drum controlling
    left/right movement:
    1.       25 Meters
    / 100 = .25 Inches
    2.       2 Inches /
    .25 = 8 MOA
    3.       8 MOA /
    .50 =16 clicks to sight windage knob in left direction for needed horizontal
    movement of grouping on target
    Is the math too much? Here’s an alternative no-math zeroing means. Using the military 25
    meter M16/M4 sight-in target (NSN 6920-01-395-2949), which uses a grid to
    graphically indicate sight adjustment clicks necessary to zero rifle for 300
    meters, the M16-A4/M4 can be zeroed without doing any arithmetic.  Still, because sight adjustment for wind is estimated in MOA, practice sight adjustment using the math given, until
    confident you understand it. There are no substitutes for MOA math when sights
    need to be adjusted for wind. And, remember, if you sighted-in the M16-A4 at 25 meters,
    rather than 32 meters, you now need to turn the elevation wheel counter clock-wise
    2 clicks, which will index the 6/3 marking to the index line on the carry
    handle above the elevation wheel. Thus set, the rifle is now zeroed for 300
    meters synchronized for a bullet drop compensation function.

  9. I have a 20" barrel and my carry handle has the 6/3 drum, which is 1/2 moa per click. I want to sight in for a 100m zero. So I loosened the top part of the drum, and set it back 6 clicks from 6/3, and tightened the drum. Now I have 6/3 for 300m, back 6 clicks or -3 moa for 100m, from 100m, 2 clicks or 1 moa for 200m, 6 clicks or 3 moa from 100m for 300m on 6/3, 12 clicks or 6 moa from 100m gives me the 400m mark, 18 or 19 clicks gets me to the 5 on the drum.. this gives 9 or 9.5 moa for 500m, I'll go with the 9.5 moa since the 5 mark isn't perfectly centered on the drum, 29 clicks from my 100m zero gives my the 6/3 again on the drum for 600m or 14.5 moa, finally 19.5 moa or 39 clicks from our zero at 100m gives us 700m, and there are 23 more clicks before it gets to the top of it's range or 62 total clicks from 100m for a total of 31 moa. Does this sound about right or am I missing something?

  20. Firstly, don't buy those cheap crooked sights made on old tooling. For about 5 dollars more you can get the lightweight slim sight made on new tooling…unless you like heavier and ruggedly crooked sights.

  22. I hate to be the asshole, but you may have just gave the worst class I have ever seen on how to zero a M4. By know means am I an expert at all things M4, but I have been to a few schools and courses and a am a Drill sergeant in the army, and it is my job to teach this. Maybe I’ll make a video to show how it is actually done

  24. Umm…Why would you want to zero with the large aperture when it is less preise than he small one? I don't recall doing that in basic, infantry school, or in the 82nd. I have never done that, and rarely ever even used the large one except at night.

  25. Front sight "could" be adjusted 5mm below the flat on the front sight tower, that's part of mechanical zero according to my G.I. Maint/rebuild manual.

  28. The weapon was designed to be worked on in a combat environment b y the soldier. A bullet, a p-38 can opener or one of those combo tools that a soldier would carry around (combination pliers, screwdriver, knife, cork screw, etc. will be perfect to maintain this weapon at the user level. Mattel toy company had the contract at first, then Colt took over.

  29. Wish I watched this video yesterday. I learned I improperly zeroed my rifle yesterday with the rear elevation adjustment instead of the front, so while I was shooting accurate at 25,I don't think it's going to scale properly. Well, back to the range….

  31. A Christian guy who can't admit when he's wrong! that's sad for us Christians. Doesn't even know large and small peep share different planes, flipping to the large after zeroing with small the shots at 100 meters will be 2-4" lower depending on brand of rifle.

  32. 1 million views and teaches wrong information, you zero with small peep because large and small hole aperture are not on the same plane, switching back and forth changes point of impact. But he is an "expert" so you can't tell him anything. The United States military would NEVER teach to zero with large peep, instruction manuals from any branch of military are clear with using small peep for zeroing, sure after zeroing you can use large peep anytime you wish but for zeroing small hole is used. We tried to tell him this years ago when video came out but all he did was link us some video of him shooting trick shots(what does that have to do with anything?)…Wrong info is wrong info.

  39. Great Video for those of us who are not running fancy optics and just using the steel sights and have to check height and windage…… Zero maximum 18 shots 9 to begin with Army regulations]

  41. I thought the video was good overall, however I would not encourage anyone to use a nail on the sights when the weapon was designed to adjust the sights with an M-16 round. Using the tip of the round you can adjust the front sight easily. I used a round on the M-16 A1 on both front and rear sites. Semper Fi!

  44. When i went through basic training some shot for two hours before zeroed properly..this is the best zeroing video ive seen on utube theres alot of bad info out there this is correct ..

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