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Tripwire11
03-25-2008, 08:56 PM
Its been all most 25 years since I have carried a M16A1, my office just got 6 A1 through the military supply system for $150.00 for 6 of them. Can someone refresh me on how to set them for mech zero? They look new, never been fired, they are not new M4, but its better than what we had before, nothing. Thanks

Mstangfk
03-25-2008, 11:40 PM
where the hell did you guys find A1's?


are you sure they arent A2's at least?


(1) Mechanically Zeroing the M16A1. Mechanically zeroing the M16A1 (Figure 2-2) is only necessary when the weapon zero is questionable, the weapon is newly assigned to the unit, or the weapon sights have been serviced. If necessary, the soldier should mechanically zero the weapon as follows:

(a) Adjust the front sight post (1) up or down until the base of the front sight post is flush with the front sight post housing (2). Then adjust the front sight post 11 clicks in the direction of UP.

(b) Adjust the rear sight windage drum (3) all the way left until it stops. Then turn the windage drum back (right) 17 clicks so the rear sight is approximately centered.

Figure 2-2. M16A1 rifle mechanical zero.

Figure 2-2. M16A1 rifle mechanical zero.

(2) Battlesight Zeroing the M16A1. If necessary, the soldier should use the aperture marked "L" to battlesight zero the weapon (Figure 2-3). Tables 2-3 and 2-4 show how much one click of elevation or windage will move the strike of the round from a 25-meter zero all the way out to 500 meters.


b. The M16A2/A3 rifle (Figure 2-4) features several improvements over the M16A1. It is designed to fire either semiautomatic or a three-round burst through the use of a selector lever (SAFE, SEMI, and BURST). The M16A3 has the same characteristics as the M16A2 with the exception of the selector lever (SAFE, SEMI and AUTO) this weapon fires full automatic.


Figure 2-4. M16A2/A3 rifle.

(1) Mechanically Zeroing the M16A2/A3. Mechanically zeroing the weapon (Figure 2-5) is only necessary when the weapon zero is questionable, the weapon is newly assigned to the unit, or the weapon sights have been serviced. If necessary, the soldier should mechanically zero the weapon as follows:

(a) Adjust the front sight post (1) up or down until the base of the front sight post is flush with the front sight post housing (2).

(b) Adjust the elevation knob (3) counterclockwise, as viewed from above, until the rear sight assembly (4) rests flush with the carrying handle and the 8/3 marking is aligned with the index line on the left side of the carrying handle.

(c) Position the apertures (5) so the unmarked aperture is up and the 0-200 meter aperture is down. Rotate the windage knob (6) to align the index mark on the 0-200 meter aperture with the long center index line on the rear sight assembly.

Figure 2-5. M16A2/A3 rifle mechanical zero.

Figure 2-5. M16A2/A3 rifle mechanical zero.

(2) Battlesight Zero the M16A2/A3. If necessary, the soldier should battlesight zero the weapon as follows (Figure 2-6):

(a) Adjust the elevation knob (1) counterclockwise, as viewed from above, until the rear sight assembly (2) rests flush with the carrying handle and the 8/3 marking is aligned with the index line (3) on the left side of the carrying handle. Then adjust the elevation knob one more click clockwise.

(b) Position the apertures (4) so the unmarked aperture is up and the 0-200 meter aperture is down. Rotate the windage knob (5) to align the index mark on the 0-200 meter aperture with the long center index line on the rear sight assembly.

Gene L
03-26-2008, 12:07 AM
Its been all most 25 years since I have carried a M16A1, my office just got 6 A1 through the military supply system for $150.00 for 6 of them. Can someone refresh me on how to set them for mech zero? They look new, never been fired, they are not new M4, but its better than what we had before, nothing. Thanks

We've got a couple of those rifles, I think from DHS. They're arsenal rebuilt to as new specs.

Unlike the newer M 16 A2, the A 1 doesn't have any elevation on the rear sight. You've got to get that from the front.

The front sight is marked "Up" with an arrow, which I think is in a clockwise direction. This means to raise the point of impact, you rotate it in the "Up" direction.

The front sight is like a scew, and turning it clockwise will lower the sight and raise the point of impact. Front sight adjustment for elevation is opposite what you'd do on a rear sight elevator, BTW.

Rear sight is also marked, "R" if I remember correctly. With either sight, you have to push the detent that holds the sight in place with a FMJ round or a punch or a sight tool, if you have one, and rotate it in the direction you want the bullet to move according the the markings on the sight.

Also, you probably don't need a 300-meter zero, since the range is much shorter for practical civilian and LEO shooting.

At 25 meters, the rifle is going to shoot WAY low for a 100 yard zero, because the sight is so high up off the bore. Specifically, it will shoot about 2" low at 25, or thereabouts. For a 25 yard zero at 100, I'd start with a 2" low zero and then adjust.

A "battlesight zero" which is 300 yards will make the rifle shoot high at 100 yards by several inches.

Mstangfk
03-26-2008, 03:45 AM
agree..
id zero at 25 or 50 not 300

GGG
03-26-2008, 04:19 AM
agree..
id zero at 25 or 50 not 300

Ahh, but zeroed at 25 IS zeroed at 300 with an A2, 250 with an A1. :D

http://www.ar15.com/content/manuals/FM23-9.pdf is a handy reference.

David Hineline
03-26-2008, 04:27 AM
Remember those older rifles had 1/12 twist barrels, designed for 55gr bullets, might get away with 62grain ammo, but don't try pusihg up heavier that that.

I would just goto the range and sight them in for abouit 1" high at 100yds that will keep you within an 8" vertical A-Zone from muzzle to 300yds.

Blackdog F4i
03-26-2008, 09:36 AM
50/200 zero and load them with Federal TRU223E 55gr. BTHP

Like David mentioned, don't try to run any of the heavier OTM rounds.

Gene L
03-26-2008, 12:43 PM
I did the ballistics on the M 16, using Hornady's Ballstic calculator (an excellent tool, available on their main web site.)

A 200 yard zero is definitely the way to go. I measured the height of the sight above bore level...it's 2.5". Using the BC of a 55 gr. FMJ bullet and a velocity of 3100 fps, I got the following.

With a 200 yard zero, at 50 yo're going to be down -.2 at 100 yards, you'll be at + 1.1, and at 200, zero.

With a 100 yard zero, you'll be -.7 at 50 yards, zero at 100, and -.2.2 at 200.

Our state firearms forenesic expert did a study on the .223. A FMJ bullet tends to do a "J" turn in 12 inches of medium. This was also reported somewhat in "The Black Rifle" of about two years ago, but they added that the FMJ bullet would frequently break at the cannalure.

This wasn't reported by our FFE, but it may be so, especially with harder medium, like drywall or a winshield.

The 55 gr FMJ is very good because it's fast, and that speed helps a whole lot with the terminal damage. The bullet is instable when it hits somethign, and wants to tumble. I think this was a consdieration when the bullet was introduced; lots of military rounds were built to be instable and tumble when they hit someone. The .303 British had an aluminum nose (covered with copper) to put the weight in the rear so it would tumble. This according to the book "The British Sniper."

We use 55 gr. SP bullets, but I wouldn't hesitate to go with a FMJ after these sources have documented the effects.

With an M 4, a 55 gr bullet is by far the best choice, I think. Got to get that speed up to make the bullet do all the damage it can do, and the short barrel knocks down the FPS.

Surf
03-27-2008, 05:52 AM
50/200 zero and load them with Federal TRU223E 55gr. BTHP

Like David mentioned, don't try to run any of the heavier OTM rounds.Agreed.