A question for you smart ballistics type guys

[Guest mtsusean]

Reference zeroing an M16A2 on a 25M range.

What is the zero target height above ground if you are prone supported/unsupported?

I need a reference. Thanks

[DWARREN123]

If I remember correctly it is about 3 1/2 feet high. Does not really matter except for the angle you fire because this determines how far the bullet will go after going through the target. It is really a 25 meter/1,000 inch distance from muzzle to target or use to be.

This is from qute a few years ago.

[Guest 2HOW]

U.S. Marine Corps 25-Meter Zeroing Procedures

(By following the steps below and establishing a zero at 25 meters, your M16A2 rifle sights will be set with a 300-Meter Battlesight.)

1. Do not move Front Sight post at this time. It was set at the factory or by a previous shooter and should be very close to your zero.

2. Center the Rear sight aperture by turning the windage knob left or right. (This is called Mechanical Zero Windage.)

3. The Unmarked aperture should be up.

4. Rotate elevation knob in the Down direction (counter-clockwise). The Elevation Knob should stop Three Clicks past the 300-Meter mark (NOTE: newer rifles may be set like this do not worry about it). The rear sight should be all the way down on the last whole 'Click' before it bottoms out. This is called Mechanical Zero Elevation for the rear sight. If your range scale will not line up in the above manner, an armorer will be required to adjust the range scale for you. (NOTE: Again this really is not required - some rifles bottom out on the 3/8 [or 3/6 for carry handles]. If you really want to adjust it then see the note at the end of these instructions.)

5. Now rotate the Elevation Knob "Up" once click past the 300-Meter mark. From this point on, the rear sight elevation knob should not be moved. Any changes in elevation required in the following zeroing steps are made to the Front Sight Post ONLY.

6. Carefully aim and fire at the center of the target bull's-eye. Take your time and be sure to use the sight picture illustrated (in the Operator's Manual).

7. If your shot group is not in the Center of the bulls-eye, use the squares on the target sheet to calculate the required "Clicks" necessary to move you next shot group (Squares are 3/8" x 3/8") into the bulls-eye. (Remember that any changes in elevation are made by moving the front sight post.) The squares are numbered around the edges of the target (see the Operators Manual for an illustration of the Target) to equal the number of clicks required to move the shot group to the bull's-eye.

Barrel Length Change Per Click

20" 3/8" for Elevation

20" 1/8" for Windage

14.5"/16" 1/2" for Elevation

14.5"/16" 3/16" for Windage

8. In order to Raise your next shot group, rotate the front sight post clockwise. (one click will move the strike of the bullet one vertical square on the target sheet [20" rifle with A2 sights] - or consult the table in step 7).

In order to Lower your next shot group, rotate the front sight post counter-clockwise (one click, as above, equals one square).

Changes in windage are made with the windage knob. (Three clicks will move the strike of the bullet one horizontal square on the target sheet.)

In order to move the shot group to the Left, turn the windage knob counter-clockwise.

In order to move the shot group to the Right, turn the windage knob clockwise.

9. Carefully aim and fire another group at the center of the target bulls-eye.

10. Repeat steps 7 through 9, if required.

11. If your group is on target, your sight is now "Calibrated". To place your actual 300-Meter zero on the Rifle, you must rotate the elevation knob on click "Down". (The range scale's 300-Meter mark should now be aligned with the mark on the receiver.)

NOTE: If your rifle bottoms out at 8/3 then follow these instructions to get the sight to bottom out at 8/3 –2 clicks.

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.
   
3. Using a 1/16" Allen wrench loosen the screw (under the revealed hole) in the sight wheel 3 full turns. Leave the wrench in the screw.
   
4. Rotate the bottom half of the sight wheel two clicks clockwise. This will raise the sight body if you look at it while you’re turning it.
   
5. Tighten the Allen screw, remove the wrench, and confirm the sight bottoms out at 2 clicks BELOW 8/3. If not repeat the procedure until it’s right.

[Guest Mugster]

Actually a sight in at 200 yards/meters is pretty good with mil spec ammo. It shoots a flatter arc sightwise vs. the military 275/300 meter zero. Basically sight it in at the 50 yard line on a rifle range. This is what I do. I'm all over the place on iron at 300 yards anyway, even off the bench. Works really well with an older M16A1 style upper. Here's an article on it:

http://groups.msn.com/TheMarylandAR15ShootersSite/improvedbattlesightzero.msnw

[DWARREN123]

The 25 meter/1,000 inch zero, at the time I zeroed, put you dead on again at 250 or 275 meters. Can't remember that far back.

[Guest Todd@CIS]

mtsusean...you didn't specifically ask about zero distance, but the thread kind of drifted that way. If the following doesn't apply, please disregard.

We recommend a 50/200 zero vs. 25/Military zero. As seen below, and as Mugster stated, a 50/200 provides a much better trajectory. Essentially, you never have +/- 2.5" out to 225 yards with this zero.

I realize you have a 20" and we used a 16", but it makes the point.

A 20" will perform even better.

Regards

ZERO

16” AR-15 with 55gr. 5.56mm M193 (approximately…always verify with live fire).

50 YARD ZERO* (recommended)

Range (yards) Point of impact

0 -2.5”

25 -1.1”

50 ZERO

75 +0.9”

100 +1.4”

125 +1.7”

150 +1.6”

175 +1.2”

200 ZERO

25 YARD ZERO

Range (yards) Point of Impact

0 -2.5”

25 ZERO

50 +2.2”

75 +4.2”

100 +5.9”

125 +7.3”

150 +8.3”

175 +9.0”

200 +9.3”

Edited February 6, 2008 by Todd@CIS

[Guest mtsusean]

Todd, I understand what you are saying, and the reason, thanks.

My question is, (and I wish I could explain this graphically) is a matter of point of aim equaling a "zero" height at both 25 meters and ~375 meters (I think that was what FM 23-9 said)

If I'm laying prone and zeroing on a 25 meter target that is 2.5 feet off the ground, I have point of aim, lets call it X. This results in a point of impact at Point A.

If I'm laying prone and zeroing on a 25 meter target is 4.5 feet off the ground, I have point of aim, lets call it Y. This results in point of impact at Point B.

Both can't be correct to have an equal point of impact at ~375 meters. There is only one correct answer. The more elevation I impart to the muzzle, the more my trajectory and point of impact changes. If I make corrections at 25 meters, I'm falsely making corrections at my "zero" height at 375 meters. Matter of fact, may not even hit the target at that point since there are some mathematical formulas that explain this.

Kind of hard to explain without showing it graphically. My spidey instinct tells me there is an answer for it. A Field Artillery solution is to hit a target by either changing elevation of the tube, changing the powder charge or a combination of the two (in the simplest terms). Since I can't change the charge of 5.56, I have to define my elevation/trajectory of the round. There are no major changes in elevation on a typical range so we don't need to compute things like Site and Angle of Site. That's when things really get hard.

[Guest mtsusean]

so it's not all about the grouping. That's important as well. But "zeroed" is not zeroed unless vertical and horizontal errors across a three dimensional plane are fixed. We want to minimize, or remove if possible, all non-standard conditions.

[Guest Todd@CIS]

If I'm laying prone and zeroing on a 25 meter target that is 2.5 feet off the ground, I have point of aim, lets call it X. This results in a point of impact at Point A.

If I'm laying prone and zeroing on a 25 meter target is 4.5 feet off the ground, I have point of aim, lets call it Y. This results in point of impact at Point B.

No practical difference when obtaining a zero, in my experience.

What's the difference in distance from muzzle to target, at 25M, when you raise the target by just two feet?

Nothing really, and that's the key to obtaining a "zero."

Both can't be correct to have an equal point of impact at ~375 meters. There is only one correct answer. The more elevation I impart to the muzzle, the more my trajectory and point of impact changes. If I make corrections at 25 meters, I'm falsely making corrections at my "zero" height at 375 meters. Matter of fact, may not even hit the target at that point since there are some mathematical formulas that explain this.

They wouldn't both be correct because you are shifting you're POA (point of aim) at 375M.

Try both zero heights as you describe above.

After both are obtained, shoot at 375 with each. You won't notice a difference between the two.

If I'm totally missing your boat, sorry.

Regards

Edited February 6, 2008 by Todd@CIS

[Guest Mugster]

The 25 meter/1,000 inch zero, at the time I zeroed, put you dead on again at 250 or 275 meters. Can't remember that far back.

Pretty sure its 275 meters with a battlesight zero of 25 meters. Although I remember holding dead on to hit a 250 meter pop up. I always tried to aim at the head of the 300 meter target.

[Daniel]

i was looking at my last qualification score card with the M16 yesterday and i would get my 300s, 250s, 200s, 150s, & 50s, but i would miss most of my 100 meter targets. anyone know why?

nvm i think it was a paper target so it wouldnt apply and i guess i just pulled all of them somehow.

[Guest mtsusean]

Pretty sure its 275 meters with a battlesight zero of 25 meters. Although I remember holding dead on to hit a 250 meter pop up. I always tried to aim at the head of the 300 meter target.

Figure 2-43. M855 drop during 25-meter zeroing

(M16A2 at 8/3+1; M4 at 6/3).

[R1100R]

On the standard M16/M4 the zero target is set for 300 meters.

The improved method that was discussed earlier in this thread does work. It is more

practical for most shooting.

I ran down to supply room and they are 300 meters. M4 on one side and M16A2 on the other. The grids were different for each

Edited February 6, 2008 by R1100R
wrong info

[Guest Mugster]

Actually, 250 and 300 are both right. 250 for A1 sights. 300 for A2 sights. I like the A1 sights alot better than the A2 sights anyway.

http://www-rucker.army.mil/a1210/Promotion/board%20questions/rifle.htm