Everything You Wanted to Know About ARs, but Were Afraid to Ask
- 1: Description
A lightweight, air-cooled, direct impingement gas-operated, magazine-fed rifle designed for either automatic or semi-automatic fire through use of a selector lever.
Caliber: Originally .308 was the caliber of choice when the AR10 was designed, which uses the direct impingement gas system very effectively with less wear and tear on the components, but was scaled down to 5.56x45 to meet the military's need for a lighter weapon system than the M1 Garand and M14 service rifles. Now there are multiple calibers which have been developed for the platform or the AR platform adapted to use.
Different Models: Airborne, what's the difference between an A1, A2, A3, and A4? The most obvious difference is the carrying handle/rear sight of the A1s, A2s, and A3s in comparison to the flat top receiver with a picatinny rail on the A4s. The other difference is that the A1s and A3s are full auto where as A2s and A4s are three round burst. Here's a by order list of differences followed by the different models of the M4.
AR10: One of Eugene Stoner's original designs and the predecessor to the AR15. Because NATO was adopting the 7.62x51/.308 round (known as the .30 Light Rifle in the late 40s) most arms developers were putting their focus towards building a weapon around the round which would be used by Western forces. FN designed the FAL off of the Nazi StG44 7.92x33 Kurz round and was persuaded by the US to adopt the 7.62 caliber over England's smaller .280 British round and was given the test name of T48 where as what became the M14 was known as the T44. Stoner wanting to move away from the old steel and wood firearms became set on showing what new space age materials could do. By the time he completed his prototype the military's testing had already been going on for two years. Despite this, the AR10 had a strong showing. It was more accurate despite being two pounds lighter and had better recoil control, however George Sullivan doomed the weapon when he tried his new composite barrels which ultimately blew up during testing. There are no AR10 "standard" specifications because it was never adopted by the military and thus never given military specs (or Milspec), thus most AR10 parts made by different manufacturers today usually won't function properly together as they all try to set the standard for the .308 AR.
AR15: After the demise of the AR10, ArmaLite restructured and sold the rights to the weapon system to Colt. Colt converted the AR10 platform to the smaller .223 Varmint round with a 1:14 RH twist with much success. However, due to the design of the pointed lead round and the slow barrel twist rate this caused the round to tumble at less than a hundred meters. Because of this tumble, and the structure of the rounds which caused massive fragmentation, this helped create reports of large wound channels from the original ten AR15s sent to Vietnam by ARPA (Advanced Research Projects Agency). Secretary of Defense Robert McNamara now had two conflicting reports, one from the Army saying it wasn't suitable for combat operations and another from the front lines of Vietnam with pictures showing its devastation. McNamara ordered another side by side test of the AR15, M14, and the AK47 by the Army, and again the Army said the M14 was their rifle. McNamara then sent the Army Inspector General to check the findings who also reported that the M14 was their rifle. McNamara becoming frustrated with the Army's incestuous relationship with the M14 caught a break when manufacturers reported they could not meet the demand for the M14 causing McNamara to halt all production of the M14. In steps Colt with it's cheaper and easier to manufacture ARs which were the only weapons which met all of the requirements across all of the branches of the military. McNamara found his universal military rifle. Colt created two AR15 variants, the 601 (to meet the demands of the Air Force) and the 602 (to meet the demands of the Army), these became the M16 (601) and the M16A1 (602).
M16: Triangle handguards, "duck bill" three pronged flash suppressor, solid buttstock with no cleaning kit storage, no forward assist, 1:12 RH (right hand) rifle twist, and slick sided chrome bolt carrier group.
M16A1: Adoption of a birdcage flash suppressor, forward assist, notches in the bolt carrier group to facilitate the forward assist, the bolt carrier group's outside was parkerized instead of chrome plated, barrel bores were chrome plated and later fully lined, a crimp was added to the cam pin so the bolt couldn't fit if it were backwards causing failures to eject, and a rib was added around the magazine release button so it couldn't be pressed on accident while closing the ejection port cover.
M16A2: Most notable difference is the switch to three round burst, but the system's not perfect because you have to complete the cycle for the sear to reset. For instance if you only let two rounds fire while in burst, the next time you squeeze the trigger only a single round will fire. Other changes included the introduction of the cleaning kit compartment in the buttstock, the barrel was given a faster 1:7 RH twist rifling, was thicker on the end to prevent bending, the front sight was made into a square allowing it to be adjusted with a loose round, the rear sight was made so you could adjust windage without a tool and could move it vertically to dial in different ranges, the A2 birdcage flash suppressor was created with a closed bottom so as not to kick up snow or dirt while firing, handguards were made symmetrical and rounded so people with smaller hands could better hold them, the pistol grip got a notch for the middle finger and texture was added, and the case deflector was added.
M16A3: An A2 with an A1 full auto assembly. Referred incorrectly as the auto version of the A2 with a picatinny rail, HOWEVER, the reason why I continue that here is due to the fact that most manufacturers have adopted the description and you will see flat top receivers referred to as "A3" receivers. The reason this happened was because the Navy had adopted the full auto version of the A2 as the A3 for the SEALs, but Colt wanting to push more military sales ended up calling the A4 the A3.
M16A4 or M16A4 MWS: The Colt "A3" that introduced the picatinny rail in place of the carrying handle. Came with an attachable A2 carrying handle, a rear back up iron sight (BUIS), and Knights Armament Co RAS handguard (the fore end rails) thus making it easy to attach vertical grips, lights, lasers, and optics and giving it the name "Modular Weapon System" or MWS.
XM177, Commando, or CAR-15: The final variant of the CAR-15 was full auto, had an 11.5in barrel, a longer flash/sound suppressor, and were mostly issued in small numbers to everyone but the infantry as a personal defense weapon (PDW). In other words, they were well suited for pilots, artillery men, and the like because they were considered mostly a defensive weapon for people who didn't need an assault weapon but something with a higher round count than a pistol.
M231 Firing Port Weapon (FPW): The first "pistol" like configuration because of its lack of a butt stock. Meant for firing from the ports of armored vehicles and only capable of firing in full auto, it has a higher cyclic rate because it fires from the open bolt position rather than the closed bolt position like your typical M16. It is also commonly used by Mech Infantry for clearing trenches and urban close quarters combat (CQC).
There were other variations, mainly a sniper variant that never really made it into wide circulation.
M4 and M4A1: Both are 14.5 barreled versions of the M16A4 with a telescoping stock, the only real difference between the two are the fire control assemblies, M4s are three round burst and M4A1s are full auto.
Milspec Vs Commercial: Airborne, what's the difference? Milspec parts tend to be a bit smaller than commercial parts making the interchangeability among the two difficult. For instance milspec trigger assemblies use small holes for their retention pins, where as commercial assemblies tend to use larger pins so it's easier to identify commercial and milspec parts. Essentially think the difference between metric and inches, similar concept. This is important to know so if, for instance, you wanted to switch an A2 stock with a telescoping stock, you need to know if your lower is Milspec or Commercial so you can buy the right size buffer tube and there by purchase the right size butt stock. Personally, I usually only use Milspec parts. It doesn't necessarily mean the parts are better, but they're made to a standard and can be mixed and matched easier among manufacturers. Not to mention they're combat tested so I know they work.
- 2: Components
The parts to an M16/AR15 by disassembly group. If you're in, or were in, the military you'll notice the Auto Sear Assembly is missing from the diagram, that's because AR15 lower receivers don't come with the holes necessary to put a standard auto sear in.
Note: In the case of a collapsible stock you have the Buffer Tube, Recoil Spring, Buffer, Receiver Plate, and Lock Nut (AKA Castle Nut). In the case of an A3 Upper Receiver (AKA Flat Top Receiver) you won't have a carrying handle unless the rifle comes with the attachable handle. Instead you will have a section of Picatinny or Mil(itary) Std(Standard) rail.
- 3: Function
Here's an old Department of the Army video in two parts that details the function of the M16/AR15. One note about the second part, as most AR15s don't have the bolt carrier or auto sear necessary for full auto or three round burst, you can ignore the last bit of the video unless you're curious how it would work. A quick look at your AR15s lower receiver and you should notice that it lacks the hole for the auto sear above the safety selector switch, if not I'm an interested buyer if you want to sell.
Part 1: http://www.youtube.com/watch?v=C2x8Oot- ... re=related
Part 2: http://www.youtube.com/watch?v=5ui288P4 ... re=related
- 4: Operating and Maintaining
I'm putting these together because there's a lot of instruction on this which can be found in Sections 2 and 3 of the Army TM which can be found here:
http://www.scribd.com/doc/3458887/Field ... -and-M16A1
Note: I will be adding videos of your's truly going through the motions at a later date.
- 5: Full Auto/Three Round Burst
It is possible to own a full auto M16/AR15, however because of the 1986 ban on full auto weapons made after 1986, you would be hard pressed to not only find one, but it would also cost you as much as a small car. If you can do that, all it takes is the $200 Tax Stamp and clearance from BATFE. You might've heard about a DIAS or rDIAS which stands for Drop In Auto Sear or Registered Drop In Auto Sear. An RDIAS is a registered machine gun and falls under NFA regulations requiring a $200 Tax Stamp from BATFE made pre 1986, these are legal to own and use with an AR15 to make it full auto, but they also cost around eight grand. A DIAS generally refers to an unregistered DIAS which can get you into a bit of trouble, i.e. Federal Pound You in the Ass for a Long Time Trouble (FPYALTT). They're also known as "Pre-81" DIAS because prior to 1981 there was a legal get around that allowed you to legally build, own, and use the DIAS without registering it because it wasn't considered a machine gun. BATFE caught on and changed that. So now what does that mean for you? It means you can find them around the net or in Shotgun News for around $150, but it is a felony to own one if you also own an AR15 or equivelant. If you don't own an AR, drop $150 on a useless and potentially liberty threatening piece of metal all you want.
So if you want to convert your AR to full auto, find a registered and transferable DIAS, eight grand is a lot less than spending personal time with Bubba.
You also need a full auto disconnect lever, a full auto safety selector switch, and a full auto bolt carrier to complete the conversion. The disconnect lever for full auto is slightly longer so it's disengaged during the firing process by the full auto safety selector switch which has multiple flat sides (instead of one like an AR15) to do so. The bolt carrier must have the full auto shelf on the bottom so it trips the auto sear to release the firing hammer at the appropriate time.
Picture of three different types of BCs. The top is your typical AR15 BC, the middle is a colt SP1, and the bottom is your standard M16 BC.
As you can see on the M16 BC it has more material on the bottom, this is the sear shelf and what trips the auto sear during auto or burst fire, and this is the kind of BC that manufacturers are referring to when they say they sell "Full Auto Bolt Carriers." Again, this does NOT make your AR full auto, and it is perfectly legal to have a full auto BC instead of your typical AR BC that lacks the shelf.
Lightning Links: They function much the same as a DIAS but I'm still learning about these, more to follow.
You can find information for timing a DIAS or Lightning Link here: http://www.quarterbore.com/ar15m16/index.html
- 6: 14.5in Barrels
So you might be asking, "Airborne, how can my AR have a 14.5in barrel when the legal limit to not register it as a Short Barreled Rifle (SBR) is 16 inches?" Most manufacturers, and DIYers, get around this by welding the flash suppressor directly to the barrel there by extending the barrel's length to the legal 16 inches. This is known as 14.5PA or "Permanently Attached (Flash suppressor)." If you don't have the flash suppressor PAed then you have an SBR and you need to register it with BATFE. Just weld the damn thing, barrels don't cost that much and you can get gas blocks/front sights that clamp onto the barrel instead of having to be slid on.
- 7: .223 Remington, 223. Wylde, 5.56 NATO and How They Play Together
"Airborne, I got this sweet .223 Remington Varminter, can I fire 5.56 NATO surplus ammo in it?" Unfortunately, you're stuck with just the .223 Rem, bud. Before I get into specifics for those interested, here's a quick compatibility reference. You can fire 5.56 NATO and .223 Rem in both 5.56 NATO and .223 Wylde barrels, it is NOT recommended to fire anything but .223 Rem in .223 Rem barrels as you can cause catastrophic damage to the barrel and possibly yourself. Now allow me to explain. To achieve the velocities required by the military the 5.56 has a larger powder charge than a .223 which creates a significant amount of pressure on the chamber and barrel due to case expansion which is why 5.56 barrels have wider throats than .223 barrels to handle the expansion of this pressure. 5.56 rounds are also slightly larger than .223 Rem rounds and can increase the rate of barrel wear or just get outright stuck depending on the fit of the bore which can cause the rifle to explode if firing in successive shots. .223 Wylde on the other hand is the middle ground between the two chamber sizes. It has a smaller throat than a 5.56 and a wider throat than the .223 Rem allowing both rounds to be fired safely and accurately. .223 Rem can be fired from a 5.56 barrel, but be warned you can end up with Failures to Eject (FTEs) because not enough gas tends to travel down the gas tube since it has a habit of escaping around the round itself due to wider bore and its casing due to the wider throat of the chamber.
- 8: Twist Rate, Barrel Length, and Bullet Weight
The twist rate is how many inches a groove in the rifling takes to wrap the entire barrel. So if you have a 1:7 Right Hand twist that means the grooves twist to the right and complete their rotation every seven inches. General gun philosophy is the faster the twist rate (the less number of inches to make a rotation) the better stabilization of the bullet since the twist causes the bullet to spin. With pointed ammunition this is most important because the front of the round tends to be heavier than the rear which will eventually cause it to tumble on it's axis or in other words flip end over end significantly degrading the possible distance it can go and it's accuracy. Heavier bullets tend to favor faster twists, because surprise you can over spin a bullet, especially lighter bullets. This is another reason you want to use barrels designed for the caliber you plan on shooting the most so you can get the most out of your rounds. 5.56 barrels tend to be 1:7 twist to maximize the weight of the M855 5.56 62gr. bullet used by the military. .223 Rem barrels tend to have 1:9 twist barrels to better maximize their typically lighter 55gr. bullets. Remember how I said the .223 Wylde is the go between the other two rounds? Guess what its twist rate is. That's right, 1:8 twist. These are the standard twist rates you'll see, you might see a 1:12 running around once in awhile.
Barrel length is really dependent on the manufacture, but typical gun philosophy says, and despite what your wife might say, longer is better. This is really an opinion and dependent entirely on what you plan to do with the weapon. For accuracy and harder hitting rounds longer does tend to be better, and here's why. Longer barrels give gases behind the bullet more time to build pressure causing the round to have a higher velocity when it leaves the muzzle of the weapon there by making it travel further and harder than it would from a shorter barrel. Due to this barrel manufacturers of short barrels continue to play around with the diameter of the bore making the tolerances tighter to help get the same amount of pressure behind the round. Now the reason why I said this matters depending on what you plan on doing there's a trade off. Longer barrels are good for accurate shots, so hunting, competition target shooting, and sniping in open areas would be your main considerations, however what if you're inside or you plan on using your AR as a home defense gun or you live in a heavily wooded area or just generally don't have a lot of open space? Why would you need a much longer and heavier weapon for that situation? That's where the short barrels come in. If you're staying within 300M with your shots and you need to not only be able to move around quickly, but also maneuver the weapon around obstacles and in tight spaces (like furniture or corners), why would you want a longer heavier weapon when you're not going to use it for it's intended purpose? When considering a barrel length, consider what you plan on using it for, that should be your main concern.