A2 vs A3 vs A4?

[Rugerlvr]

Here's my A4 styled semi-auto:

 

[ochmude]

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]

My first thought on seeing the 0-2 was that it was larger for a larger FOV on short range targets.

 

[chauncey]

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]

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.:

 

[Bartholomew Roberts]

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 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]

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]

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]

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]

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 sell same-plane aperture sights for the A2? 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]

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]

Most likely A3. You can mount a carry handle or optics of your choice.

 

[RockyMtnTactical]

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]

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!!!!

 

[Bartholomew Roberts]

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]

FM 23-9 M16 A1 and A2 Marksmanship July 1989

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]

US Marine Corp MCRP 3-01A 29 March 2001

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]

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]

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]

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]

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]

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]

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]

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]

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.