A2 vs A3 vs A4?


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groover000
April 11, 2008, 12:28 AM
I have tried searching for this but I am getting no results. What is the differences between an A2, A3, A4 on ar-15 rifles? Pics would be helpful if you have them. Thanks in advance.

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Matt-man
April 11, 2008, 01:03 AM
According the military designations of the M16 series:

A2: Fixed carry handle. Safe/Semi/Burst fire control group.
A3: Fixed carry handle. Safe/Semi/Auto fire control group.
A4: Detachable carry handle/flat-top receiver. Safe/Semi/Burst fire control group.

AR-15 vendors frequently get A3 mixed up with A4 so you often see flat-top ARs called A3s.

Check out the Wikipedia entry for the M16 (http://en.wikipedia.org/wiki/M16_rifle) for additional info.

BBroadside
April 11, 2008, 04:49 AM
So for ordinary civilian (i.e., semi-auto-only) purposes, the A2 and A3 are much the same? I see people making references to "A2 style sights" so now I guess they're contrasting them with A1 rather than A3/4-style sights.

Here's a pic of an A2 sight (http://www.coloradoshooting.org/10.jpg).
And a (frustratingly small) one of an A1 sight (http://www.bushmaster.com/images/catalog/Parts_Accessories/Gunsmithing/A1_RSITE_ASSY.gif).

Incidentally, I ran into the Civilian Marksmanship Program's competition rules (http://www.odcmp.com/Competitions/M16.htm) on the subject today. Looks like removable carry handles are okay; it's just the "flat-top only" upper that are a problem. Also it implies that the A1 has a short buttstock than the later ones (not mentioning telescoping buttstocks which I gather aren't really M16 items per se, but rather CAR-15 / M4 furniture).

DMK
April 11, 2008, 07:49 AM
Matt-man's got it. For civilian rifles, A3=A4. The A3 is a misnomer really. Civilian manufacturers came up with it before the military adopted the M16A4.

I see people making references to "A2 style sights" so now I guess they're contrasting them with A1 rather than A3/4-style sights.
A1/SP1 rifles have a round front sight post with 5 adjustment clicks.

A1/SP1 rifles have a rear aperture with two small holes. One is set higher than the other so you can flip the sight back and forth for a close range and a long distance zero. The rear sight is not otherwise elevation adjustable. The windage adjustment must be made with a tool or the tip of a round, and it locks in place.

All later rifles (A2/A3/A4) have a square front sight post with 4 clicks.

All later rifles with both fixed (A2) and detachable carry handles(A3/A4) have a rear aperture with one of the holes much larger (a ghost ring). You can still flip the aperture back and forth for a close range and a long distance zero, but the close range sight is the large ghost ring. The rear sight is elevation adjustable with a large range marked ring below the sight. The windage adjustment are made with a thumbwheel.

When one refers to A2 sights, they are referring to the later sights, or merely the later aperture or front sight post.

Vice versa, when they refer to A1 sights.

It gets really confusing when you refer to military contract carbines. Before the M4 carbine was standardized (which uses A2 sights BTW), Colt designed carbines with a seemingly random combination of features.

Another point of confusion is front sight bases. Military M16A4s and M4 carbines use taller 'F' marked front sight bases. This is because Colt designed the removable carry handle to be taller, (not because of barrel length which is what many folks say is the reason). Most civilian rifles, flat top or not, use standard height front sight bases. Some companies, like CMMG offer 'F' height sight bases as an option. With a standard height sight base and a carry handle, you may require a taller front sight post. Often times not.

Creature
April 11, 2008, 08:18 PM
A2 is on the top, A3 is on the bottom:

http://www.innovativetactical.com/catalog/images/bushmaster/b74u4s91h09.jpg

A4 as descibed by Matt-man.

Bartholomew Roberts
April 11, 2008, 08:48 PM
Creature, your description is incorrect. Technically speaking, since we are discussing military nomenclature, the top rifle is not an M16A2 and the bottom rifle is not an M16A3.

However, even if you were just using the term loosely to describe the upper receiver, the top one would be an A2; but the bottom would be an A4.

Matt-man described the military nomenclature and the manufacturer confusion very well.

Matt-man
April 11, 2008, 09:03 PM
I stole these photos from FN. They have the rifles labeled correctly, which is no surprise since they produce them for the US military.

M16A2:
http://www.icantping.com/~mmasuda/images/boom/m16a2.gif

An M16A3 would look just like this except it'd have a "FULL" position on the selector instead of "BURST."

M16A4:
http://www.icantping.com/~mmasuda/images/boom/m16a4.gif

You often see A4s accessorized with things like optics, like this:
http://www.icantping.com/~mmasuda/images/boom/m16a4.jpg
USMC M16A4s get a Knight rail system like the one shown here (this is actually an AR-15, it doesn't have a 3rd position on the selector).

pgeleven
April 11, 2008, 11:25 PM
You can still flip the aperture back and forth for a close range and a long distance zero, but the close range sight is the large ghost ring
wrong. the larger ring is for night shooting when your pupil diameter increases you are not able to use the day sight (smaller ring). its not a 'ghost ring for close range'

DMK
April 11, 2008, 11:35 PM
wrong. the larger ring is for night shooting when your pupil diameter increases you are not able to use the day sight (smaller ring). its not a 'ghost ring for close range' No, I'm right. The larger ghost ring is lower than the smaller peep. It is a close range sight. The small peep, being higher, is for long range use.

Soldiers are taught to look over their sights for night shooting.

pgeleven
April 11, 2008, 11:45 PM
according to TM 9-1005-319-10 (our operators manual) its a night sight. we aim with the muzzle for close range, both soldiers and Marines. regardless, the sight doesnt need to be lower, it will hit a 30 meter target on the same level as a 300 meter target.

41magsnub
April 11, 2008, 11:48 PM
Soldiers are taught to look over their sights for night shooting.

We were taught to use the larger ring for night fire and while in MOPP gear in the Army...

We zeroed with the smaller ring.

DMK
April 11, 2008, 11:50 PM
OK, so maybe it is used at night too.

The two apertures still zero at different ranges, with the larger one zeroing closer than the smaller one.

pgeleven
April 11, 2008, 11:56 PM
we never zero'ed with the larger ring, it would contradict all PMI's on sight picture/sight alignment that we have ever been taught. don't take this as a pissing match DMK, its the first rifle i had in the military and carried for almost a decade. i almost felt like you were telling me something about my wife that i knew wasnt true.

DMK
April 12, 2008, 12:15 AM
we never zero'ed with the larger ring,I never said one should zero the rifle with the large ghost ring.

What I said was that the ghost ring is lower than the small peep. If you zero with the small peep (as you should) and flip to the large aperture (without changing the elevation ring), your POI will be lower. ie, the round will cross zero at a closer range with that aperture than with the other.

For example, I use an A2 aperture on my M16A1 upper. I zero the rifle with the small peep at 200 meters (219 yards), IBZ (http://groups.msn.com/TheMarylandAR15ShootersSite/improvedbattlesightzero.msnw). When I flip to the ghost ring, I get an approximately 100 yard zero.

My only point was simply that the apertures are different heights when you flip them. Maybe this isn't the way the .mil tech manuals describe it, but it's true. Try it yourself if you doubt me.

Onmilo
April 12, 2008, 09:00 AM
I qualified numerous times on the Army Rifle Qualification Course which has pop up targets to 400 meters.
You use the fine apeture and shoot from a foxhole position after zeroing the rifle with the fine apeture using the twenty five meter zeroing target.

Qualifying on the Army Combat Rifle Course, I was taught to move and shoot at pop up targets to ranges of no greater than 125 meters.
You are instructed to use the large apeture sight as a ghost ring and this is after prone fire zero of your weapon using the small apeture and 25 meter zeroing target.

Qualifying on the Urban Warfare Combat Rifle Course featured live fire in tire houses with ranges no more than forty feet and you are taught to look over the rear peep and aquire the target with the front post only.

Bear in mind I qualified on these courses twenty five years ago but knowing the Army, not a whole lot has changed.

The M16A4 flat top is arguably the best version of the long rifle to date.
The burst fire selector is not really necessary because everyone is taught to use the rifles as semi auto.

Creature
April 12, 2008, 10:27 AM
Creature, your description is incorrect. Technically speaking, since we are discussing military nomenclature, the top rifle is not an M16A2 and the bottom rifle is not an M16A3.

However, even if you were just using the term loosely to describe the upper receiver, the top one would be an A2; but the bottom would be an A4.

Matt-man described the military nomenclature and the manufacturer confusion very well.

I stand corrected. Thanks!

How is it that the majority of folks in the civilian AR industry have it all wrong when it comes to describing A2 and A3 uppers...and why does it persist?:

http://www.ar15.com/lite/topic.html?b=2&f=186&t=147417

http://cmmginc.secure-mall.com/shop/index.php?shop=1&cat=30

http://www.bushmaster.com/products.asp?cat=6

DMK
April 12, 2008, 10:51 AM
How is it that the majority of folks in the civilian AR industry have it all wrong when it comes to describing A2 and A3 uppers...and why does it persist? They aren't incorrect when describing A2 upper receivers. The fixed carry handle with the elevation wheel is identical to the upper on the M16A2. Although, if you really want to get technical, an A2 upper assembly should not have an HBAR barrel. It would have a 20" Govt. profile (lightened under the handguards) with a 1/7 twist and chrome lining.

As far as civilian A3s are concerned, the civilian manufacturers started selling flat top uppers before the military adopted them on rifles (although they may have had them on carbines already, I'm not sure when Colt started shipping flat top M4s). There were only the A1 and A2 rifles, so the marketing folks decided to sell flat tops as A3 rifles (because it sounded cool to them, like tactical does today). Once a term gets widely used in this industry, it's hard to shake.

Are they wrong? They make the rifles, so who's to say. They could market them as Martian ray guns if they wanted. The differences between 'real' military M16A2 and M16A3 Assault Rifles is moot because all new manufacture civilian ARs are semi-auto.

Here's an AR15 clone of an 'M16A2'. I could call this an AR15 clone of an 'M16A3' too. The military M16A2 and M16A3 look identical. This same rifle with a flat top receiver (removable carry handle) would be an 'A4', but could be referred to as an 'A3' by some manufacturers of civilian rifles. Confusing? yea.
http://mysite.verizon.net/dmk0210/myarms/AR15A2.jpg

aloharover
April 12, 2008, 11:12 AM
Bear in mind I qualified on these courses twenty five years ago but knowing the Army, not a whole lot has changed.

So you were using the M16A1 not the A2?

FWIW rifle ranges at Benning, Stewart, Hood, Polk, Irwin, Lewis, Schofield, Dix, Ap Hill, Indian Town Gap, and Drum are all 300m Pop-Up.
The Army FM on Marksmanship has listed the course of fire tables since the 1970s as 50-300ms
The Army popup qualification course has you shoot 20rds from the foxhole, and then 20 prone unsupported.

Bartholomew Roberts
April 12, 2008, 01:14 PM
How is it that the majority of folks in the civilian AR industry have it all wrong when it comes to describing A2 and A3 uppers...and why does it persist?:

My guess is that the M16A3 is a very obscure designation. I think it is only used by the Navy and there are very few in existence. As a result, most manufacturers were probably not aware it existed. So when the flattop came along as the "next generation" upper in the early 90s, a lot of them started calling it an "A3" upper.

I think it continues to persist because a lot of people use that term for flattop uppers now and the M16A3 is still an obscure weapon.

chauncey
April 12, 2008, 01:23 PM
but the close range sight is the large ghost ring

hate to tell you, but "pgeleven", who must be a jarhead, is correct.

your confusion may be based upon some earlier battle rifles, like the Savage-produced Enfield, that has a 300-yard aperture and a 600-yard aperture. the elevation of the sight changes, but I can't remember if the size of the peep gets bigger or smaller.

I can recall, that when shooting while wearing a gas mask, it didn't matter what sight I used, I couldn't hit squat. night shooting wasn't much better.

DMK
April 12, 2008, 01:37 PM
Chauncy, I don't know what they were teaching you folks in the military, but the elevation does change when you flip the A2 aperture.

There is a large aperture for low light/close in (< 200M) shooting and a small aperture used for longer range shooting (300m+).
http://groups.msn.com/TheMarylandAR15ShootersSite/whatisana1a2a3ora4.msnw

Q: Can I use the A2 aperture on my A1 Rifle?

A: Courtesy of Forest

Yes! In fact it’s recommended. By using the A2 aperture instead of the A1, you gain a large ‘ghost ring’ for close quarters shooting, and a smaller hole for precision/long distance shooting. ....

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

FAQ # 4

AR-15/M-16: Rear Sight Elevation Shifts and the need for a Same Plane Aperture Sight

As originally designed the AR-15/M-16 sight system adjusts for windage at the rear assembly and for elevation in the front to zero the rifle to the individual shooter. To obtain the ballistic adjustment needed for longer range shooting the original rear sight had one aperture higher than the other. While this system would not give the shooter an exact elevation adjustment for a specific range, it would under battle conditions put the bullet close enough for government work so to speak.

The new A2 rifles and carbines employ a rear sight system that includes a range cam to allow the shooter to more precisely adjust the ballistic arc to their needs. This system eliminated the need for an elevation shift between the large close quarters aperture and the smaller long-range aperture. However the aperture shift is still with us today.

Comparing some of the rear sights available today there appears to be 3 variations available. The 1st style (and oldest) has a .014 offset. This gives a 2.52 inch shift in point of impact at 100 yards between the two apertures. The 2nd style has a .017 offset, which shifts point of impact 3.06 inches at 100 yards. The 3rd style has a .024 offset giving a 4.36 inch shift in P.O.I.

All of the points of impact shifts shown above are for the standard barrel AR-15/M-16 that has a sight radius of 20 inches. The shorter sight radius (14.5 inches) of the M4 carbine and weapons of similar configuration increase the amount of point of impact shift. The shifts for these shorter sight radius weapons are 3.48, 4.25, 5.96 inches respectively.

The only reason for the various shifts would be for changes in the ammunition used by the military over the course of this weapons employment.

Most people are completely unaware of this elevation change that occurs when the aperture is shifted from one to the other. They just figure that their rifle is doing something strange.

Our aperture sight for this weapon has both the large and small apertures on the same plane so there is no difference in the point of impact when you shift from one to the other. We have also offset one of the apertures by .007 to make up for the sideways movement of the aperture on the windage screw as it pivots.

By installing our same plane rear aperture you now can sight in your rifle using the smaller aperture and shift back and forth between the two apertures as your light and range needs change without having to do mental gymnastics to know where your bullets impact will be.
http://www.xssights.com/faqs.html#faq4

Take a look at the XS Sight systems "Precision Tactical Rear" aperture (http://www.brownells.com/aspx/NS/store/ProductDetail.aspx?p=24977&title=AR-15/M16%20HIGH%20VISIBILITY%20REAR%20APERTURE%20SIGHT&s=239#239). It's a "Same Plane" sight. They sell this as a replacement for the standard A2 aperture because the latter will change your elevation when you flip it.

http://www.xssights.com/store/tactical.html

rangerruck
April 12, 2008, 01:46 PM
I am going to sound stupid and chime in here, so I guess it may be our point of reference. When I joined the army, we still had the a1, and were transing to the a2. I can remember many, many times, that shooting instructors, mostly DI's, specifically told us that the larger app ring was for fast acquiring, and closer up shooting.

Onmilo
April 12, 2008, 02:14 PM
Correct, they were M16A1 rifles.
The only experience I had with the M16A2 was a repair course that dealt with the installation and maintenance of the burst fire mechanism and the installation and removal of the A2 rear sight assembly.

Every Qualification I did was 40 rounds from the foxhole supported position and the maximum range I am sure was 400 meters.
I only remember firing from the prone position for the 25 meter zeroing and during the Combat Rifle Course, I cannot ever remember firing from the prone during the Standard Rifle Qualification. HTH

cdbruster
August 18, 2008, 01:59 PM
During my time in the USMC, I was instructed by PMI's, senior Marines and likewise passed down to junior Marines that the aparture (ring) with the larger inside diameter is for low light conditions and closer ranges. The aparture with the smaller ID is for brighter light and longer range engagements. There really is no cut and dry rule as to when you have to use one or the other. If you are taking a 75 yard shot and it is very bright outisde, it may be prudent to use the smaller aparture. The pros of each are. Larger Aparture: quicker sight picture and good for low light conditions. Smaller Aparture: more acurate sight picture and good for more intense light. I have never been told the center line of one aparture is higher or lower than the other therefore rendering different range BZO's. If that were true, what is the elevation know used for? Rhetorical Question, don't answer that bacause there is no elevation or aparture centerline difference from the larger to the smaller. What I want to know is what is the sight height difference between the A4 (M4 Carbine) and the A2, A3. It seems the A2, A3 have lower profile sights than the A4 (M4). Does anyone have any information?

Tarvis
August 18, 2008, 03:41 PM
Now, I am not an expert, nor in the military. That being said, here are my observations: It seems like the M16's operator manual would mention something about an elevation difference between the two apertures. I haven't read the operators manual, but it sounds like the large ring is meant for low light which doesn't have a whole lot to do with elevation. The civilian market doesn't know very much about military guns, mostly because they don't sell them. More importantly, the civilian market doesn't sell military guns. A guy at a gun show once told me that BUIS makes a good fold up iron sight. I thought about telling him it was an acronym for Back Up Iron Sight, but I figured he'd get it sooner or later.

I'd say the best way to figure out if your rear sight has a different center for each aperture would be to get out your caliper and measure each hole.

Another thought: it could be possible that the elevation between the two appears to change due to a different sight picture, caused by changing the sight alignment for each aperture.

Rugerlvr
August 18, 2008, 03:50 PM
Here's my A4 styled semi-auto:

http://www.xmission.com/~jdjonsson/images/a4-1.jpg

ochmude
August 18, 2008, 04:07 PM
Just thought I'd add my $.02 into the whole "what is the larger sight for" debate. As I was taught in the Marines, the larger sight, which we called the "Oh-Two Sight" since it has a "0-2" stamped underneath the aperature, was for rapid target engagement at ranges from zero to 200 yards....hence the 0-2. For longer ranges, you use the smaller aperature and 8/3 small gap (or 6/3 small gap for the A4). The 0-2 sight could ALSO be used in low light and when in MOPP, but that is not its explicitly designed purpose. Mind you, this is based on verbal instruction, not reading of a TM or FM, and therefore could simply have been bad word. It does make sense, though, based on the stamp on the aperature.

Tarvis
August 18, 2008, 04:47 PM
My first thought on seeing the 0-2 was that it was larger for a larger FOV on short range targets.

chauncey
August 18, 2008, 07:45 PM
Chauncy, I don't know what they were teaching you folks in the military, but the elevation does change when you flip the A2 aperture.

if this is wrong, then sorry, but what I was trained in both university-level Army ROTC (instructors were prior service) and USMC boot camp was incorrect. nothing against the MD site you referenced, but does anyone have a copy of the USMC or AUS TM manual for the M16A2 (or A1 for that matter) that can reference the manual for an answer?

Dave Markowitz
August 18, 2008, 07:52 PM
Civilian flat tops may be A3s, but they are AR-15A3s, or another similar designation. They aren't M-16A3s, so saying that referring to a civvie AR-15A3 is incorrect, is incorrect. (How's that for confusing?)

E.g.:

http://i30.photobucket.com/albums/c340/davemarkowitz/AR6721/DSC00010.jpg

Bartholomew Roberts
August 18, 2008, 10:06 PM
if this is wrong, then sorry, but what I was trained in both university-level Army ROTC (instructors were prior service) and USMC boot camp was incorrect. nothing against the MD site you referenced, but does anyone have a copy of the USMC or AUS TM manual for the M16A2 (or A1 for that matter) that can reference the manual for an answer?

You don't need a manual to find out the answer. Take an M16A2 to the range and flip the aperture without changing the elevation wheel, you'll get a different point of impact because the apertures are set to different elevations.

However a quick look at the zeroing process in any military manual (www.ar15.com/content/manuals/TM9-1005-319-10.pdf) will also confirm the elevation change (Hint: Why does the manual have you change the elevation wheel during the 25m zero when flipping between the small and large aperture?)

cdbruster
August 19, 2008, 10:05 AM
I put my detachable carry handle back on my m4 last night and mounted my aimpoint on the quadrail free float tube between the rear sight and front sight. I zeroed the rear sight (using the small aparture) so the aimpoint dot was setting right on top of the front sight post when the front sight post was centered in the rear sight aparture. Once it was zeroed, I turned off the aimpoint, flipped over to the 0-2 (large) aparture, placed the front sight tip in the center of the rear sight aparture and turned the aimpoint on. The Aimpoint dot was setting in the exact same place it was when using the smaller aparture. This tells me there is no difference in the height (with respects to centerline) from the small to the 0-2 apartures. This is true for A2's and later models however the A1's didn't have an elevation knob and used apartures with different height for different ranges. Some of the BUIS being sold today implement the idea used on the A1's because to make them compact or fold out of the way, there is no room for an elevation knob. My GG&G Folding BUIS' 0-2 aparture sets lower than the smaller aparture. My DPMS non-folding BUIS does have an elevation knob and the 0-2 and smaller aparture co-witness the aimpoint dot in exactly the same place as did the carry handle sight.

ERock45
August 19, 2008, 10:33 AM
Roughly and clearly speaking.

Clearly the purpose of the larger apearature is 0-200 yards. It says so on it. The smaler sight picture is for the 300 yard "monster line" (10 shots-10 seconds for MARINE QUAL.) and 500 yards (or meters, depending on the range you're at.) This is what we are taught in basic training at Camp Pendleton from time Immortal. I know, I shot 247 of 250 on pre-qual day( a Thurs.), and 243 of 250 on qual. day.( a Fri.). This is a MARINE RIFLEMAN'S instruction, how the Army is instructed and trained to shoot is an entirely different doctrine.

You maybe able to use the smaller aperature for low light conditions and the larger for bright daylight, but that is not their intended purpose.

This was back in the day, when we had the M126a1 and were transitioning to the M16a2s'. I shoot better now with the A2's I have.

WPNS 2/1
1st Mar Div
Camp Pendleton Calif.

chauncey
August 19, 2008, 07:11 PM
You don't need a manual to find out the answer. Take an M16A2 to the range and flip the aperture without changing the elevation wheel, you'll get a different point of impact because the apertures are set to different elevations.

However a quick look at the zeroing process in any military manual will also confirm the elevation change (Hint: Why does the manual have you change the elevation wheel during the 25m zero when flipping between the small and large aperture?)

my comment wasn't meant to be smart. I am genuinely asking what, if anything, the TM says about it. I don't have a TM for this weapons system, and I don't think point of impact is a reliable way to answer the question. I also don't have access to my M16A2 anymore, since I turned in my weapons card in 1999.:)

This is what we are taught in basic training at Camp Pendleton from time Immortal.

if this covered during instruction on the West Coast, it must have been during all the free time you guys had, since you never had to push.;)

Bartholomew Roberts
August 19, 2008, 09:47 PM
This tells me there is no difference in the height (with respects to centerline) from the small to the 0-2 apartures.

1. If there is no difference between the two apertures, then why does everybody and their brother (http://www.slr15.com/slr15riflerearsiteaperature.html) sell same-plane aperture sights for the A2 (http://www.brownells.com/aspx/ns/store/ProductDetail.aspx?p=26607&title=AR-15/M16/M4%20A2-STYLE%20BACKUP%20IRON%20SIGHTS)? If the aftermarket sights are marketed as "SAME PLANE" what does that suggest about the standard sights? If the standard sights are on different planes, what does that imply about changed point of impact?

2. If there is no difference in the height of the aperture, why does the USMC manual that I linked to above tell you to adjust the elevation wheel when switching between the large and small apertures?

3. Finally, why does your point of impact change up to 4-5" at 100yds depending on what aperture you are using when you use A2 sights and a 16" barrel and do not adjust the elevation wheel?

I don't think point of impact is a reliable way to answer the question.

You don't think where the bullet goes is a reliable indicator of whether or not the rear sights are on the same plane? If that is the case, then I doubt anything I can write, link-to, etc. will convince you.

Shoot how you like then and one day you will shoot enough to figure it out.

cdbruster
August 20, 2008, 12:55 AM
Yes, I understand TM9-1005-319-10 instructs that the 0-2 aperture does render a 200 meter zero when the rifle has a 300 meter BZO with the smaller aperture. My previous post was stating my observations in respects to the orientation of the aimpoint dot between the 0-2 aperture and the small aperture. A 62 grain 5.56 X 45mm NATO Ball Round will impact just over 8 inches high if engaging a 200 meter target with a 300 meter zero. With this being said, the 0-2 aperture centerline would have to be .067 inches lower than that of the smaller aperture. So, what is the 8/3 or 6/3 minus 1 setting on the elevation knob used for? I distinctly remember using the 8/3 minus 1 setting on my A2 when in the Corps.

shooterfromtexas
August 20, 2008, 12:57 AM
Most likely A3. You can mount a carry handle or optics of your choice.

RockyMtnTactical
August 20, 2008, 03:09 AM
In military rifles, the designations are usually fairly straight forward. With the commercial market, who knows... A3 and A4 are practically interchangeable for most commercial purposes and denote a flat top upper.

chauncey
August 20, 2008, 10:40 PM
You don't think where the bullet goes is a reliable indicator of whether or not the rear sights are on the same plane? If that is the case, then I doubt anything I can write, link-to, etc. will convince you.

a peep sight relies on the ability of your brain to center the top of the post in the center of the aperture. as the aperture gets larger, it is more difficult to accomplish this act of centering. so no, I don't think my brain's ability to center the post in a larger aperture offers a definitive answer to this question.

nor do I think I could shoot 4 out of 5 bulls at the 200 yard line, standing, with the larger aperture in place. I doubt I could hit crap at the 300 or 500 with the larger aperture, either, regardless of rear sight elevation. what you are suggesting is that if I flip up the larger aperture and adjust the elevation of the rear sight I should hit at the same point of aim. I disagree. that goes nothing toward the original question of relative elevation of the apertures on the charging handle, just my brain's ability to center the post in the aperture.

btw, my brain seems to do fine with this, using the smaller aperture, as long as it's not muddied by frustration over someone jumping into my crap for wanting to see a TM instead of believing everything I read on the internet!!!!:cuss:

Bartholomew Roberts
August 21, 2008, 07:58 AM
btw, my brain seems to do fine with this, using the smaller aperture, as long as it's not muddied by frustration over someone jumping into my crap for wanting to see a TM instead of believing everything I read on the internet!!!!

One reason the Internet is an unreliable source of information is that anybody can participate. This is why one of my roles as a moderator is to try to spread good information and mitigate the spread of bad information. For example, we can have somebody claim that the USMC and Army ROTC teach that there is no change in elevation when you flip the aperture. Backed up by these noted authorities, a reader might assume that this is in fact true.

However, this is plainly wrong to anyone with even a little common sense who has actually fired the weapon. As cdbruster noted, if you have a 300m battle zero and flip to to the large aperture, you now have a 200m zero. This is why the 200m zero is marked "0-2". Clearly, if you were zeroed at 300m and are now zeroed for 200m with just a flip of the aperture, then flipping the aperture changes elevation.

This is plain, simple deductive reasoning that doesn't rely on a TM or someone's inability to use iron sights with enough accuracy that they can discern the difference between a 4-5" change of point of impact.

As for frustration, if you think it is frustrating to be reminded of all the reasons your statement was questionable after you had already been given the link to the TM demonstrating this in the first link, then just imagine what it is like to be the guy doing it.

Wolf 117
September 1, 2008, 10:23 PM
FM 23-9 M16 A1 and A2 Marksmanship July 1989
Page 3-25, 3-26 M16A2 Standard Sights and Zeroing.
The larger aperture, marked 02 is used for moving target engagement and during limited visibility. The unmarked aperture is used for normal firing situations, zeroing and with the elevation knob for target ranges up to 800 meters.

Same manual as above, page 3-24 The aperture marked L is for ranges beyond 300 meters and the unmarked or short range aperture is used for ranges up to 300 meters.

Hers the deal when I was in. M16A1 Short range aperture was used most commonly 250 meters, rarely did we use the L marked aperture, we adjusted by holding slightly over or under as the situation demanded.

Enter the M16A2.
Once Battlesight zero was completed, we left the 0-2 sight down and only used it for limited visibility (near dark), after dark the IR lasers were used with PVS 7's, or PVS 4's. On occasion in certain places in the world we would use the elevation wheel for longer than 400 meters. But most often the M-21 would take care of the threat.

Note: This was from the A1 to A2 transition and doctrine is in a continual process. Some of what a few Marines stated here seems to ring a bell also....
I'll see what else I can dig up.

Wolf 117
September 1, 2008, 10:38 PM
Bingo!

US Marine Corp MCRP 3-01A 29 March 2001

Page 9-2 Para 9003

The rear sight consists of two sight apertures, a windage knob and an elevation knob. See Fig 9-4. The large aperture marked 0-2 is used for target engagements during limited visibility, when greater field of view is desired or for engagements of targets closer than 200 yards/meters. The unmarked aperture (small aperture) is used for zeroing and normal firing situations.

falcon195
April 8, 2009, 11:18 PM
OK so maybe this is going to offend some of you but here it goes.
I think the different apertures do give elevation changes.
Why would the large aperture be marked 0-200 if this aperture didn't give a different POI than the small aperture?
Maybe the TM and instructors didn't give this information because for the majority of situations this POI change really didn't make much difference in normal situations.
So then maybe they didn't want to confuse you with this information as you no doubt were thinking about drinking and women more than how your rifle actually worked. Or maybe they figured the average grunt didn't have the smarts to understand this.

Dogbreath
December 2, 2009, 04:22 PM
Don't forget the A2 added a brass deflection block as A1s put brass into left handed shooters mouths. In A1s early days left handed shooters became 60 gunners. Also dmk is right on with the elevation different on the A2 sights he even post a thread from the manufactor explaining the reason, and the measurments also that when floors it would change the windage and how the offset the windage by .007. I have put thousands of rounds down range with A2 carry handles M4s. A2 carry handle M16s, and A4 flat top M4s and A4 M16s. Like the man said take your rifle out and shoot it id you don't see the change them you have no buissness being in the buissness. I can see where different people would be taught to shoot with the big ring at night. And the small during full light. I have no problem saying that is a good pratice, but to say the are not different down range is crazy. And yes I have put hundreds of rounds down range at night too.

Dogbreath
December 2, 2009, 04:46 PM
The aim point thing makes sence because it's MOA is so big. I could see that an aim point has like a 4 MOA at 100 meters

TexasRifleman
December 2, 2009, 04:55 PM
Taken straight from TM9-1005-319-10.

This really isn't that complicated.....

Notice that the 0-2 position is ONLY aligned when the elevation is all the way down.

Flipping to the other sight should bring the sights in alignment at 300 yards so they are absolutely NOT same plane sights by default.

Quentin
December 2, 2009, 05:54 PM
DMK and others above are correct, the small aperture should be used for battlesight zeroing of 300 meters and you will be about 6" high at 200 meters. When you flip to the 0-2 aperture you now have a 200 meter zero as long as the elevation wheel is left on 8/3 or 6/3. (It also is used for low light conditions and the odds are that you won't be going for 300 meters then.)

Of course you can use the Improved Battlesight Zero and reindex the elevation wheel for two clicks under 8/3 or 4 clicks under 6/3 to have your cake and eat it too. Use the small aperture for the 25/300 meter battlesight zero or click down to 8/3 -2 or 6/3 -4 and use the small aperture for a 50/200 meter zero. Best of both worlds.

KungFuNerd
January 25, 2012, 10:33 AM
Zombie thread

About the Flip sights
I don't know ANYTHING but happen to be reading the Army manual from 1985
As an aside, there LOTS of spelling errors in these :)

They list two different sights
"Standard Daylight Sighting System" and "Low Light Level Sighting System"
The Standard Daylight uses the unmarked Aperture for 0-300m and one marked "L" for greater ranges.
The Low Light Level System has a 7mm aperture for low light and a 2mm for normal.
The Low Light Level System also has a Tritium Front Post

The 1986 Manual lists two Apertures
One for 0-200m and the other for 300-800m
The Larger Short Range Aperture is only used when the Rear Sight is all the way down
The Smaller Aperture is unmarked and is the "Normal Range" aperture and is used to Zero

Later in the Manual "Shooting in low light or close range"
Lower rear sight to 300m setting and Flip Aperture to the sight marked 0-2 ( the "Oh Two" sight mentioned in an earlier post)

Ramone
January 25, 2012, 01:47 PM
Back on the OPs questions;

The M16(nothing) had no forward assist, and un chromed bores

the M16A1 got a forward assist , a compartment in the butt stock for the cleaning kit, chrome bore, and IIRC, some mods to the BCG to slow the cyclic rate (but the BCGs were still interchangeable. At some point, the flash hider changed, too. the lower receiver got the raised area surrounding the mag release button.

The M16A2 got a heavier Barrel, a flash hider/compensator (same as the A1, but with the lower holes omitted) a Brass Deflector (just that little bump on the upper in front of the Forward assist) Improved sights (adjustment for both windage and Elevation on the rear, 4 click square front post) Better Handguards, a slightly longer (3/4"?) butt stock, and a 3 round burst instead of auto. The 3 rd burst sucked, BTW- it was a good idea, but if you feathered off only one or two rounds the next pull of the trigger got only 2 or one rounds- and the trigger pull changed wildly at each of the stops. it also got tighter rifling (1:8?).

I never saw an M16A3, though we were told we'd get 3 per squad. As far as I know, It was the M16A2 with full auto instead of Burst.

The M16A4, I understand to be an M16A3 (FA) with a Detachable carry handle.

I was issued an M16A1 and later an M16A2- the rest is just my recollection.

Edited to Add:

there is a good rundown of the variants here:

http://en.wikipedia.org/wiki/M16_rifle

FIVETWOSEVEN
January 25, 2012, 02:16 PM
I believe an A2 sight and just the sight alone is a detachable carry handle. A2 uppers have a fixed, non-detachable carry handle while A3 uppers have a railed upper and no sights.

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