DC AR-15 Buyer's Guide (In Progress)

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If you’ve been here for any length of time, you’ve probably seen a title including the words "Which AR?" at least a couple times every couple months. This is notable for a couple reasons. First, it tells us that many people are buying AR-15s for use as a home defense tool. Second, it tells us that there is not a centrally-located knowledge base for people to look at to help them decide which rifle to purchase. It is my hope that this guide can fill that vacancy and be useful for readers on the hunt for an AR-15.

Since this is a buyer’s guide, it will share overlap with jwise’s outstanding complete AR-15 buyer’s guide. If there are any mistakes or incorrect statements, let me know and I'll fix them.[/i]



Appendix:

• Part 1 – Introduction
• Part 2 – Key Components
• Part 3 – Explanation of Gas Systems
• Part 4 – Support Components
• Part 5 – Ancillary Stuff
• Part 6 – Ammunition
• Part 7 – Maintenance
• Part 8 – Cost/Benefit and Example Builds
• Part 9 – “The Chart” and what it means
• Part 10 – Further Reference Material

Note: Over the course of the next week I'll be fleshing this out in its entirety. I'm going to focus on finishing the ten sections first, and then backtrack and edit in relevant pictures. Please bear with me and I'll do my damnest to make this worthwhile.


-Brian

[DefensiveCarry.com]

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Part 1 – Introduction


The purpose of this guide is not to argue the merits of the platform. It is not to debate handgun versus long gun use for home defense. And most of all, it is not to bicker about brands. It is the purpose of this topic to help readers determine how to select from the vast array of makes and models available a rifle that suits their home-defense needs.

Before we actually get down to brass tacks, I need to clarify something. Everything from here forward will rest on the singular assumption that you intend to take this rifle into harm’s way, or want a rifle capable being taken into harm’s way. To use a rifle “in harm’s way” means to actively face deadly force: if your rifle fails, you or others may die. I have nothing at all against recreational shooters, but this guide is not meant to help someone buy a rifle that only comes out for a match or some weekend plinking.

Understand that the rifle is a machine, a tool. We have expectations for how our tools ought to perform and under what conditions, and this is no less true with a rifle chosen for home defense. Because this is a tool we will be entrusting our life to, it needs to be absolutely reliable. Our goal is to eliminate the rifle as a variable in why things might go wrong. The less time spent on fixing the rifle, the more time can be put into shooting it.





(Continue to Part 2)

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Part 2 – Key Components


What makes a good, reliable rifle? There are a number of components that are more critical than others in producing a reliable rifle. Broken bolts, poorly staked carrier keys, incorrect chamber specs, a weak extractor spring, the castle nut slipping off, or the wrong buffer for the gas system will all stop your rifle in a hurry. For our purposes, this means we ought to prioritize the whole bolt carrier group, the barrel, and the buffer assembly.


Bolt Carrier Group

A brief overview of what bolt-related failures look like can be found here in the 2006 NDIA Small Arms Symposium, SOPMOD Program Overview (search “bolt failure”). Generally, harsher firing schedules will wear bolts out between 3,000 and 6,000 rounds. Milder firing schedules may extend bolt life to 10,000 rounds. Additionally, Bill Alexander (Alexander Arms: Welcome to the Revolution) points out here that poorly made bolts will wear the barrel extension unevenly, potentially creating excessive headspace. Excessive headspace leads to case head separation with sub-optimal brass (not an easy malfunction to fix). Buying good bolts is a must, and keeping spare good bolts on hand is a smart idea.

Staking the bolt-carrier key screws correctly is one of the easiest things to do, and yet is so seldom done. A gas key that shoots loose will cause short-stroking, turning that fine AR-15 into a single-shot rifle. Rob at VA Arms created an excellent topic on M4C (here) showing what proper carrier key staking looks like. If your carrier key staking doesn’t look like this, it needs to. Staking tools are available from Ned Christiansen, and many reputable gunsmiths (G&R Tactical, VA Arms, etc) will do it for a small fee.

The last part of the bolt carrier group we care about is the extractor assembly. A weak extractor in the AR-15 causes the extractor claw to slip off the rim of the cartridge. This will result in a failure to extract the spent brass from the chamber. These problems are exaggerated in a carbine-length AR-15. Crane developed an extractor upgrade kit in response to this, and since then so have several other companies. MGI’s D-ring has been extensively tested by Crane and is also a good upgrade option. For carbines, the black insert is what you’re looking for (which you’ll see in the links provided).


Barrel

The barrel has been accurately called the heart of the AR-15. It’s the single most expensive component of the rifle and is the part that directly influences the bullet as you send it downrange. It’s what determines a rifle’s service life. Unfortunately, it is also the subject of more voodoo than any other part of the platform; this is discussed in some detail by K.L. Davis here.

Currently, the list of characteristics to look for in a fighting barrel usually looks something like this:

• Mil-B-11595E chrome-moly vanadium steel
• 1:7 rate of twist
• chrome-lined bore and chamber
• proper 5.56 NATO chamber
• HPT/MP Inspected

Basically, a mil-spec M4 barrel. Pretty simple. 11595E CMV steel is durable and handles heat well, chrome-lined bore and chamber resist corrosion better and makes cleaning easier, proper chambering and testing/inspection ensures safety of use, and the 1:7 twist will shoot anything you could want to shoot. You’ll get this out of most BCM, Colt, and LMT barrels and barrel assemblies.

With this in mind, one particular a number of folks out there have brought to market cold hammer forged barrels. CHF barrels are generally much more durable than standard barrels and have significantly longer service lives, albeit slightly more expensive than non hammer-forged barrels. Bravo Company, Centurion Arms, Daniel Defense, and Noveske all make some of the best barrels in the industry. For stainless steel, Lothar Walther’s LW50 barrels are probably the best stainless steel barrels one could purchase for an AR-15 in terms of fighting-rifle durability and match grade accuracy, with Noveske’s stainless steel barrels running a close second. I’m willing to bet the LW50 barrels will be more accurate than the CMV barrels, but they’re more expensive to start and will get even more expensive once you have them cut down to a more manageable length.

This segues nicely barrel contours. Lately there has been a trend in the market toward lighter-weight barrels, especially among high-volume shooters. With participation in carbine courses increasing, people are getting a better feel of what it’s like to move an HBAR barrel around for hours at a time. I won’t recommend any particular contour, but I will say that there is always a compromise. The lighter the barrel, the more comfortable it is and quicker it heats up, resulting in accuracy degradation. The heavier the barrel, the less comfortable it is and slower it heats up, resisting accuracy degradation but taking long to cool. In this respect, Centurion Arms’ and Noveske’s improved barrel contours are positive deviations from the norm.

The last point on barrels is proper chambering. 5.56x45 NATO is not the same as .223 Remington. NATO ammo is frequently loaded at much greater pressures than is safe to fire in SAAMI-spec .223 Remington chambers. Hopefully I don’t need to describe to you the potential consequences of a boom too big to contain. A hybrid chamber called the .223 Wylde also exists, but I believe there are enough very accurate 5.56 NATO-chambered rifles out there to make me question the need.


Buffer Assembly

The buffer assembly in the AR-15 is to slow down the rearward-moving bolt carrier group and eventually return it to battery. There are choices between mil-spec and commercial receiver extension tubes, a variety of buffers and action springs available, and misconceptions of how to keep the whole thing together.

First, terminology: buffer tube and receiver extension tube are synonymous, as are buffer spring and action spring. Yes, the latter in both examples is technically the right way. No, it’s not worth worrying about.

Mil-spec versus commercial tubes – there are more differences than just the names, and in building a fighting rifle we do have a preference. K.L. Davis describes them in detail on M4C here. Put simply, the diameter of mil-spec tubes is greater in the threading than in commercial tubes, despite the commercial tubes’ greater diameter past the threading. Why do we care? Commercial tubes will not fully engage the threading in the receiver, which can allow the tube’s threads to pull away from the receiver. No joy. It’s not a common failure, but an easily avoidable one. Get a mil-spec buffer tube. If you’re using a rifle/A1/A2 tube, you’ve nothing to worry about since they’re all the same.

Buffers and action springs are a bit broader in scope. Everything you could ever want to know about the different buffers and what length action springs you want can be found here. However, I strongly recommend first running what comes with the gun. Only change something after you find your rifle short-stroking or overcycling (gas port variances between guns play a big role here). Too heavy and/or too long an action spring will cause short-stroking (bad), and too light a buffer and/or too short an action spring will cause overcycling (also bad). Over time the gas port will erode, allowing more gas into the action and changing the cycling behavior. In addition to replacing an action spring worn too short, switching to a heavier buffer might also be beneficial. Seek balance you must, young Jedi.

Finally, how to keep it all together. If you’ve got a fixed-stock assembly, you’re again in luck. Screwing the stock in place is the most you have to do. If you have a collapsible stock, however, things change a bit because we now have a castle nut. Castle nuts are meant to prevent rotation and hold something in place, and have slots or cuts meant to be filled with material to accomplish this. That material is meant to come from the receiver end plate. An unstaked castle nut will eventually back off and come loose. Once it comes loose, so too does the stock it was holding in place. Collapsible stocks will rotate freely at this point, doing two things: annoying the hell out of you, and backing off enough to allow the rear takedown pin’s detent spring to escape. A jostle, rough bump, or similar motion is all it would take for the rear takedown pin to disappear and open your rifle up. Here is what you want to stake, courtesy of Rob from VA Arms.

Loc-Tite is a common and very poor substitute for staking the castle nut. It’s a pain to remove if you want to swap stocks, especially if you want to reuse the same buffer tube. Staking is easy to apply, easy to remove, and receiver end plates are cheap.





(Continue to Part 3)

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Part 3 – Explanation of Gas Systems


As anyone who has been around AR-15s for any length of time can attest to, there are a lot of different configurations for this family of weapons. Everything from short-barreled CQB weapons and full-sized rifles all share the same basic operating system, but that operating system is modified depending on what the user is trying to accomplish. Gas ports (the area on the barrel where propellant gas is siphoned off to work the action) differ in location and size. Barrels may be extremely long or quite short. This is a brief description of the main three gas systems and why they’re used. I’ll be excluding pistol-length systems because they really don’t matter to us as defensive tools.


Carbine

Originally developed for the Colt Commando’s 11.5” barrel, the carbine length gas system is probably the most prolific gas system for the AR-15. For short barrels, it works great; something to consider for those willing to jump through hoops to obtain a short-barreled rifle. However, when set up on the longer 14.5” and 16” carbines (such as the M4 Carbine), it is a very harsh system for the rifle. Heavier buffers and bolt upgrades were developed to help slow the system down, but it truly does work best with shorter-barreled rifles. Carbine-length handguards are 7” in length if they stop at the front sight base. Handguards of 9” in length or more will cover the gas block. For home-defense and law enforcement use, it is hard to imagine a better rifle than a short-barreled AR (keeping in mind that the shorter the barrel, the greater the muzzle blast).


Midlength

The youngest of the AR gas systems, midlength gas systems were developed specifically to address the harshness of the carbine-length system on 14-18” barreled rifles. The gas port is set two inches further than the carbine system, resulting in a smoother extraction cycle, a longer sight radius, and more real estate to grab onto in terms of handguards. Midlength handguards are 9” in length if they stop at the front sight base. Handguards of 11” in length or more will cover the gas block. For non-SBR carbines with barrels 14-18”, the midlength gas system is the way to go. The ideal home-defense or law enforcement carbine where SBRs are not allowed, or where you don’t feel like doing the paperwork to get one, would be a 16” barreled middy or 14.5” barreled middy with a permanently attached flash hider.


Rifle

The rifle-length gas system is the original gas system for the AR-15, featured on the venerable (It’s 50 years old, I can say that now) M16. This is the smoothest of the AR gas systems, meaning the easiest on parts and having the lowest pressure curves. The only real downside to the system is that without a modified gas port it requires an 18” or longer barrel, which is getting too long for home-defense and most law enforcement patrol rifle use. Rifle-length handguards are 12” in length if they stop at the front sight base. Handguards of 13” or longer will cover the gas block. Some have toyed with the idea of cutting down rifle-length barrels to 16”, which would give the smoothest system possible on a carbine, but with the popularization of the midlength gas system and the potential gas port adjustments needed to make a rifle system work with a 16” barrel, it would be easiest to just get the middy if a carbine appeals to you.





(Continue to Part 4)

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Part 4 – Support Components


Support components are those things that are also important to your rifle but don’t directly influence its function; things that you can take on or off at will and expect the rifle to still work the way it’s supposed to. Handguards can help with accuracy, cooling, and provide attachment points for lights and additional grips. Magazines are necessary to feed the thing. Weaponlights help you ID your target, and sights and optics help you actually hit your target. A muzzle device can make or break your game plan once the trigger is pulled. Whether slings are necessary on a home-defense long gun is debatable, but they certainly have value for law enforcement (and are typically required in carbine instruction courses).


Handguards

There are three main criteria people select handguards by: whether they’re free-floating, how securely they mount and can be mounted to, and how much they cost. A “free float” handguard is one that does not contact the barrel, and thus one that does not change point of impact if the weapon is positioned up against something or a sling is used as a firing aid. The accuracy benefit of free-floating is lost in a home-defense scenario, but law enforcement might find it advantageous to rest their rifle up on a barricade or their car without having to worry about an altered point of impact. Security, durability, and cost needs no further description. Daniel Defense and LaRue Tactical are currently top-dogs in the AR quad-rail handguard market, but a more complete list of the different handguards can be found here, although it does not include the JP/VTAC modular handguard and the VTAC Extreme / Troy TRX Extreme handguards (the same, just slots vs holes). It is possible to mount weaponlights without having to purchase an aftermarket rail, saving you quite a chunk of change if that is the main reason you’re buying a handguard, but options are more limited.


Magazines

Saying magazines are important is a lot like saying water is wet. It’s obvious. However, the AR wasn’t designed to feed from curvy 30-round magazines, but from straight 20-round magazines. Fortunately, technology has progressed a bit and today we have a lot of choices for good, reliable magazines. Right now the best magazine available is the Magpul Pmag. It is probably the most durable and reliable AR-15 magazine money can buy, and certainly is the most durable and reliable mag at its price point ($10-15). Buy them, they will not disappoint. Other good choices include the Lance L5 and TangoDown ARC. If plain ol’ USGI magazines are more your speed, Bravo Company sells Brownells and D&H Industries magazines with Magpul Enhanced Followers and your choice of chrome-silicon or stainless steel mag springs. Right now they’re selling most of their AR-15 magazines at half or almost-half price, which is a friggin’ steal.


Lights and Light Mounts

For any gun meant for “social use”, consider a weaponlight to be mandatory. How often have we heard on the news someone getting shot late at night by their loved one after being mistaken for a burglar? Do you think there might be unarmed bystanders in a suspect’s home?

There are too many good lights, and ways to mount them, to get into specifics on each. I will say that Surefire is one of, if not the, most popular manufacturer of weapon lights; other popular choices include Insight Technologies, Pentagon, and Streamlight. Where and how you mount a light will depend on how you plan to grip the weapon. Pressure pads can allow you to mount a light further away from your grip while still being accessible, but they’re costly. Ideas on how to mount weaponlights can be found here. Regardless, get a light and get training with it. Many well-known and reputable training outfits offer a low-light / no-light specific course (as with Surefire Institute) or include low-light / no-light components within their other courses.


Muzzle Devices

By and large, the USGI birdcage flash suppressor is sufficient for most purposes. It’s fairly small, durable, and typically comes with the barrel so it costs nothing. However, in terms of actual flash suppression, it has nothing on the AAC Blackout, Smith Enterprises Vortex, and Yankee Hill Phantom, ranked in order of most to least effective. These are outstanding at suppressing the flash of the 5.56 NATO, which might not be noticeable or sound important until you have the opportunity to shoot indoors and in low-/no-light. They are also conveniently long enough to bring your 14.5” barrel over the 16” mark when pinned.

Compensators I’ll be leaving alone, and indoor shooting is why. This is also why I’d ax the newer flash hider / compensator combos. On the other hand, “blast redirectors” (for lack of a better name for them) might be quite handy for shooting indoors. I call them “redirectors” because they direct all of the blast (light and sound) downrange instead of to the sides. There are only two biggies on the market: the DPMS Levang Linear Compensator and the Noveske KX3. This is probably the one time I will ever recommend something DPMS over something Noveske. By all indications, the Levang comp works just as well as the KX3, but is smaller, lighter, and a lot less expensive (as in, a quarter of the cost). The Levang requires a crush washer, the KX3 does not.

The last type of useful muzzle device for the AR-15 is the most obvious, and probably the coolest, one: sound suppressors. They kill flash, significantly cut down the sound, are a lot larger, and cost worlds more. Good ones will run $800 and up, and virtually all suppressors are adding 16+ oz and 4-5” in overall length and to the rifle. Sound suppressors are definitely viable options for those in states where they are permitted, and for those willing to deal with paperwork and the tax stamp. A few dozen different makes and models can be found here. Tactical Operations reportedly makes some of the best suppressors you can buy, but Mike R. would prefer you called him to talk details (be sure to have some spare time...).


Slings

I am honestly conflicted on the subject of slings, and largely due to inexperience with them on my part. Many feel that a rifle without a sling is like a pistol without a holster. There is a strong argument for being able to handle a rifle more effectively with one hand while grabbing family members (or suspects) with the other, and for not having to put your rifle down to do the same. Conversely, break-ins are about speed; how fast someone can put don a sling from a dead sleep is dubious to me. I can see the argument for a police officer needing a sling, but I cannot think of a very good argument for one on a home-defense rifle. I will certainly update this as learning occurs, but right now I don’t know what I don’t know.





(Continue to Part 5)

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Part 5 – Ancillary Stuff


"Ancillary" in the context of this guide refers to those components for the AR-15 worth mentioning, but that do not directly influence the reliability of the weapon and can be upgraded to make the weapon work better for you. This is about ergonomics and how to make a rifle more effective for the person handling it. Many of the components are required on the gun for it to function (such as pistol grips and buttstocks), but all of them will add to, take away from, and otherwise change the weapon and how you use it.


Pistol Grips

For virtually everyone in the United States over the age of 5, the stock (A1 or A2) AR-15 pistol grip sucks. It’s too small, does not line your hand up naturally to interface with the trigger, and necessitates rubbing that irritating “gap” under the rear of the trigger guard. There are a lot of different grips out there that remedy this. Popular choices are the Ergo SureGrip, Magpul MIAD and MOE grips, TangoDown Battle Grip, and the brand new Stark SE-1 grip. These are all $20-$40 upgrades and are obviously very personal, but they are certainly upgrades.


Stocks

Stocks... well, truthfully there are far too many stocks to “sum up”, but there are a few companies who should be looked at if you want to migrate away from the standard A1, A2, or CAR stocks. Magpul, LMT, and VLTOR all make outstanding buttstocks, and Troy Industries has recently jumped in with their Battle Ax CQB stock. Like pistol grips, choosing a stock to upgrade to is personal. Be warned: if you choose a collapsible stock and have facial hair, expect it to be pulled. There is less available for fixed stocks, but Ace and Defensive Edge are thought highly of and are popular enough to find good reviews for.


Verticle Grips et al.

There are a lot of options for vertical grips, but they’re all designed for the same basic purpose: provide the user with better control over the weapon, more comfortably. The latter it does well – there’s not much more comfortable than the beer-can grip held out in front of you. The former, on the other hand, is questionable. Held in the beer-can style, it becomes more difficult to control the weapon along the barrel. Many users have taken to modifying their grip on the weapon such that the vertical grip is only a handstop or reference point, which led to the development of the stubby vert grips. Knight’s Armament took it a step further and developed a plain ol’ rail mounted handstop. After reevaluating how people are holding their rifles and why, Magpul also developed the Angled Forward Grip, or AFG. Whether and how one uses a forward-mounted grip, and which grip they use, is highly dependent on how the rifle is being shot.





(Continue to Part 6)

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Part 6 – Ammunition


Ammunition for self-defense is very interesting subject. It is so interesting, in fact, that people will invest energy in arguing the merits of one caliber versus another with incredible regularity. Some are well-reasoned. Most are not. Instead of simply listing good ammunition for the AR-15, we’ll first look into some of the basic mechanics of how a bullet wounds, discuss and dispel a couple popular myths, and describe a brief history of the 5.56x45. Hopefully, by the time you get to the list of “good ammo” you’ll understand why it is good ammo. Bewarned: this will be a long post.

While AR-15s can be had in a staggering number of calibers, virtually anything that can fit in the magazine, we’ll be focused exclusively on the 5.56x45 NATO. It is the most known caliber for the rifle, the best supported in terms of factory and reloading options, and has the greatest number of durable and reliable factory rifles available. It also simplifies this discussion immensely.




How Bullets Work

As I’m sure many of us know, the human body is a remarkably durable piece of equipment. It can withstand some pretty incredible traumas and still support itself well enough to fight and possibly survive. There are many stories about American GIs taking a burst of 8mm from a German MG 34 and surviving, and just as many describing German soldiers still fighting after taking half a clip of .30-06 from an American Garand. Yet, many people die every year from the diminutive .22 long rifle, and many more from small caliber pistol rounds like the .380 ACP and .38 Special. Heck, some people don’t even know they’ve actually been shot, and others drop even if they haven’t been shot!


In Transit

Let’s take a look at what bullets actually do, so we might understand the above examples and why they aren’t as complex as they might look.

A bullet leaving the barrel of a rifle is given spin by the barrel’s rifling. A spinning bullet is a lot like a gyroscope, always trying to turn the same way. Spinning bullets, like spinning gyroscopes, are harder to deflect from their path than non-spinning bullets and give the bullet a much straighter flight path. However, a lot of forces are acting on the spinning bullet: gravity, air resistance, recoil, bullet motion, and even the spinning itself. These forces cause the axis around which the bullet rotates to not be perfectly aligned with its flight path, and the bullet to wobble slightly along the way. The net effect is a very mild corkscrew-like transit. The “wobble” creates what we call yaw, or the angle of the centerline of the bullet relative to its flight path. The variance yaw will change over the course of the bullet’s flight, being greater at close ranges before the bullet can stabilize, less after the bullet stabilizes (and “wobbles”/yaws less around its axis), and greater again as it slows down enough to lose stability and deviate from its flight path.

Visual aid: spin a top on a table. At first, it wobbles a bit, and eventually stabilizes before it slows down and begins to wander more from its axis. The spinning bullet is doing exactly the same thing, only horizontally and at much greater speeds.


Upon Arrival

Now we know what the bullet does on the way, but what does it do once it “gets there”?

First, Bullets damage in basically two ways, also paraphrased from Dr. Roberts. The first is crushing of the tissue the bullet physically comes in contact with, and the second is the stretching of the tissue adjacent to the bullet’s path. The localized crush creates a space where tissue is permanently destroyed. This space is the permanent wound cavity. Formation of the permanent cavity is consistent and reliable. The “temporary” cavity is a little more complicated. Tissue surrounding the main permanent cavity is briefly pushed aside, driven radially outward by the bullet’s passage. I say “briefly” because this empty space is only empty for a moment; the elastic recoil of the tissue will subside and move back toward the permanent cavity. This is the temporary wound cavity, and is a lot harder to predict. Because most things in the body have different degrees of elasticity, it’s hard to tell what will be damaged by the stretch and what won’t be. Still, the several inelastic tissues (liver, kidney, spleen, pancreas, brain, and completely fluid or gas-filled organs) are highly susceptible to damage from this temporary cavity.

A bullet striking a person will first penetrate flesh and begin to slow down rapidly. Flesh is a lot stronger than most people realize, and will stretch significantly before it tears. It also rests on other elastic tissues, like muscle and almost everything else in the body. The sudden increase in drag on the bullet and rapid loss of velocity overcomes its rotational stability and may cause the bullet to yaw… only instead of the 0-4 degrees the bullet may yaw in flight, it may yaw more than 90 degrees. To quote Dr. Gary Roberts here:

“If the bullet yaws, more surface area is in contact with tissue, so it crushes more tissue, creating a larger permanent cavity. When a bullet yaws, it also displaces more of the surrounding tissue, increasing the temporary cavity size. Both the largest permanent and temporary cavities are produced when the bullet is traveling sideways at 90 degrees of yaw, allowing the maximum lateral cross sectional area of the bullet to strike tissue and displace the greatest amount of tissue. Longer and wider bullets have a greater lateral cross sectional area and thus create a larger permanent cavity when they yaw.”

For the readers wondering how bullet fragmentation plays into this, I’ll defer again to Dr. Roberts:

“Projectile fragmentation in tissue can also greatly increase the permanent cavity size. When a rifle bullet fragments in tissue, each of the multiple fragments spreads out radially from the main wound track, cutting its own path through tissue. This fragmentation acts synergistically with the stretch of temporary cavitation. The multiply perforated tissue loses its elasticity and is unable to absorb stretching that would ordinarily be tolerated by intact tissue. The temporary cavitation displacement of tissue, which occurs following the passage of the projectile, stretches this weakened tissue and can grossly disrupt its integrity, tearing and detaching pieces of tissue.”


Myths

There are two particular myths that I’m going to address: so-called hydrostatic shock and “knockdown power”.

Regarding hydrostatic shock: much of the support for the concept comes from the man promoting it drawing parallels between concussive blasts and the shock waves generated by a bullet impacting the limbs or torso. I have yet to see Dr. Michael Courtney, the most vocal proponent of hydrostratic shock, able to demonstrate a parallel between damage due to concussive blasts (read: bombs) and the shock wave generated by a bullets. Claims concerning neurological damage are especially questionable to me, as a college student studying the brain in particular. Incapacitating neurological damage (really any neurological damage…) due to the shockwave from a projectile impacting the limbs or torso is unheard of among both peers and professors. If hydrostatic shock existed I would expect to see more evidence in support of it given the frequently of gunshot wounds that occur in the United States and conflicts like those in Iraq and Afghanistan.

Dispelling the myth of “knockdown power” is a lot more straightforward. As FBI Special Argent Urey Patrick describes on page 9 of this outstanding article (from which I borrow the title of the next section), a bullet simple does not generate the momentum necessary to knock someone down. This is demonstrated quite clearly using simple ballistic pendulums.




The Human Target

Now that we understand what a bullet does once it hits someone and how it wounds, let’s take a quick look at what we needs it to do to a human target.

There are only two definitive methods of stopping someone with a bullet: hit their central nervous system or bleed them out. The first option produces more or less instantaneous results, while the latter can take a while. Obviously the former is more desirable than the latter; it doesn’t take a very long time or very much effort for someone, even mortally wounded, to pull a trigger. As Dr. Ken Newgard describes and Dr. Gary Roberts reports (also in the link provided above):

“A 70 kg male has a cardiac output of around 5.5 liters per minute. His blood volume is about 4200 cc. Assuming that his cardiac output can double under stress, his aortic blood flow can reach 11 Liters per minute. If this male had his thoracic aorta totally severed, it would take him 4.6 seconds to lose 20% of his total blood volume. This is the minimum amount of time in which a person could lose 20% of his blood volume from one point of injury. A marginally trained person can fire at a rate of two shots per second. In 4.6 seconds there could easily be 9 shots of return fire before the assailant’s activity is neutralized. Note this analysis does not account for oxygen contained in the blood already perusing the brain that will keep the brain functioning for an even longer period of time.”

In order for a bullet to get to the “good stuff” from any angle, it needs to be able to reliably penetrate at least 12-14” of tissue. Turn a person partially sideways, and assume one or both of their arms are outstretched toward you (as if, say, pointing a gun at you). Look at the material between you and their vitals: all of the muscle and bones in the hands, forearm, elbow, upper arm, shoulder, and the chest. Now add clothes. Even a skinny junkie or malnourished third-world insurgent will have quite a lot of “stuff” in the way of their vitals. Start stacking on muscle and it gets even worse.

As a bullet penetrates tissue and before it yaws, it leaves a narrow wound channel referred to as the “neck”. The “neck” of a wound profile is the skinny channel before the bullet fully or partially upsets to create a larger cavity. Typically, a short (less than 4”) neck is better, as it indicates early upset after penetration; in fact, our ideal wound profile will have a short neck followed by rapid expansion, a large permanent wound cavity, and reliable penetration. Remember how we want at least 12” of penetration, though? Though it may be hard to visualize, many types of ammunition in several calibers, including the 5.56, can exhibit early this upset while also providing the depth of penetration we want. The largest wound cavity will not likely extend as far back as 12”, parts of the projectile will certainly penetrate that far.






Psychology

Psychology can, and frequently does, play a role in stopping a threat, but it’s not reliable. A threat can be incapacitated psychologically but not psychologically. The same man who would collapse for fear of his assumed injuries when sober might not even notice them of he’s doped up, drunk, or high. That is to say, psychology can actually prevent incapacitation as well as initiate it. If we’re pulling the trigger, we want the threat stopped right now, or as close to right now as is possible. Relying on the psychological effects of being shot to end a threat is simply not viable.




The 5.56x45 NATO

By now you have a good understanding of how a bullet flies, how it hurts, and what we need it to do. Now we can look at the 5.56x45 NATO and perhaps put to rest some of the misconceptions about the round.


History

Immediately after the Korean conflict ended, the small-arms community buzzed at the prospect of replacing the M1 Garand and M1 Carbine. Additionally, several important events occurred that would eventually lead to the creation and adoption of the 5.56x45 NATO.

To kick it off, Britain’s Dr. Richard Beeching conducted tests similar to the United States’ 1920s pig tests and came to the same conclusion: most infantry engagements took place within 600 yards and full-power rifle rounds (our .30-06 and their .303 British) were just too powerful at those ranges. They more often went through their targets and did not injure them as well as a smaller 6.5-7mm caliber would. In 1952, Norman Hitchman’s “controlled salvos” concept evolved into Project SALVO, which suggested that a burst or volley of small-caliber projectiles can be effective at closer ranges while providing greater controllability in automatic fire. Following this, reports investigating both the potential of high-velocity .22 caliber cartridges and how infantrymen actually fight were released. Special attention was paid to the ranges at which infantry fight, especially to the poor accuracy of infantrymen at extended ranges. Except for penetration of barriers, small caliber, high velocity (SCHV) cartridges appeared superior to U.S. military .30 caliber cartridges at the ranges relevant to infantry combat. Later tests in Vietnam circa 1962 confirmed Hitchman’s previous notions about SCHV cartridges. The Marine Corp Landing force development center evaluation of the AR-15 in 1963 concluded that between the M14 and AR-15, the AR-15 would be the more effective combat rifle for the USMC; only the lack of a .223 machine gun prevented them from recommending adoption at the time.

Despite heavy institutional resistance, skullduggery, and mismanagement (mostly from the Army), the AR-15 is eventually adopted by the United States military. Whatever some may think, the 5.56x45 NATO was not selected because of its reduced terminal effectiveness (“Hurt one so he must be carried out…”) or because maximum firepower (read: most ammo) trumped all else. The SCHV concept has been repeatedly proven to be a sound one, even limited to silly Hague-compliant, non-expanding ammunition. The single biggest criticism of SCHV rounds is their poor barrier penetration, which is a valid point of concern

But it’s also pretty convenient. We civilians aren’t bound by Hague-convention nonsense, nor do we want a lot of barrier penetration. Cool huh?



Wound Characteristics of SCHV Cartridges

As noted by Dr. Martin Fackler, Dr. Gary Roberts, and others, wounding characteristics for small caliber, high velocity cartridges are someone unique. Specifically, they are more sensitive than other calibers to variations in angle of attack (AOA) and fleet yaw, bullet construction, and the target itself. This sensitivity is such that multiple people can give conflict reports on performance that are all accurate. The combination of high speed and small mass means that there is more inherent variability in performance in SCHV cartridges than there will be in larger or slower cartridges.

Remember how bullets wobble while in flight, producing varying degrees of yaw? This helps determine what’s called “angle of attack”. Angle of attack (AOA) is simply the angle at which the bullet strikes a target relative to its flight path, or the degree of yaw as it hits something. As mentioned previously, the largest variation in yaw is at close-quarter battle distances: basically 100 yards and in for the M855. Doctor Gary Roberts describes the effects of AOA variances on page 8 of his 2008 NDIA presentation. At a higher AOA, say 2-3 degrees, even FMJs provide acceptable terminal ballistics. But at 0-1 degrees, the exact same bullet will frequently pass right through the target. Where some soldiers are describing great success with the M855 and others are describing serious deficiencies, both are correct and are telling the truth. SCHV cartridges like the 5.56x45 are very sensitive to AOA differences. Open-tip match bullets are much less susceptible to AOA variances, as are some of the better bullets that will be described below.


(Images courtesy of Dr. Gary Roberts in his 2008 NDIA presentation "Time for a Change", pg8.)

Fleet yaw is another issue worth mentioning. To quote Dr. Roberts, “Fleet Yaw is the terminal performance variation caused by inherent variability in each rifle and occurs in all calibers. 5.56 mm FMJ appears to suffer more Fleet Yaw induced variability than other projectile calibers & types.” As with AOA, open-tip match and other well-made bullets are less susceptible to variances by fleet yaw. Other calibers are less sensitive to it as well.

Bullet construction and target material will sound similar to the above: SCHV cartridges are generally pickier about what they go through and how well they go through it than are larger calibers. For example:



The Barnes 70 gr TSX is an excellent bullet, but against auto glass the jacket petals sheer off and the bullet behaves something like a wadcutter. You’ll get penetration, but better choices can be had. While clothing seems to play a large role in the effectiveness of handgun rounds, it does not seem to be as important for rifle rounds. I am seeking clarification of this.




The List

Alright, alright, enough delay. What rounds are good choices for 5.56x45?

“Zhukov” at AR15.com put a lot of time and energy into compiling one hell of a defensive ammo resource here. Since it deserves recognition, and is the first time I get to be brief in this entire section, I present to you a nice, easy-to-read, too-long-in-coming list of good self/home-defense 5.56 ammo:

“If Barrier penetration is NOT an important factor AND your rifle can stabilize them (1:9 minimum twist rate):

* Hornady 75gr OTM loads
* Nosler 77gr OTM loads
* Sierra 77gr SMK loads


If Barrier penetration is NOT an important factor AND your rifle can't stabilize the heavy 70+ grain bullets:

* Sierra 69 gr SMK loads
* Hornady 68 gr OTM loads
* Winchester 64 gr JSP (RA223R2)
* Federal 64 gr TRU (223L)
* Hornady 60 gr JSP
If Barrier penetration IS an important factor
* 62 gr Federal bonded JSP Tactical (LE223T3)
* 55 gr Federal bonded JSP load (Tactical––LE223T1 or identical Premium Rifle––P223T2)
* Swift 75 gr Scirocco
* 60 gr Nosler Partition JSP
* Barnes all copper TSX/TAC-X (inferior performance through glass compared to a TBBC)


If using a short-barreled weapon AND your rifle can stabilize them (1:9 minimum stwist rate):

* 70 gr Barnes TSX/TAC-X
* 75 gr Swift Scirroco
* 75 gr Hornady OTM
* 77 gr Nosler OTM
* 77 gr Sierra SMK


If using a short-barreled weapon AND your rifle can't stabilize the heavy 70+ grain bullets:

* 62 gr Federal bonded JSP Tactical (LE223T3)
* 55 gr Federal bonded JSP load (LE223T1 or P223T2)
* 60 gr Nosler Partition JSP
* Barnes 55 gr TSX/TAC-X”

*A note on bullet-size for fragmenting and non-fragmenting bullets from Dr. Roberts:

“Keep in mind, that with non-fragmenting bullet designs, heavier bullet weights are not necessarily better, especially at closer ranges and from shorter barrels. As long as penetration and upset remain adequate, it is possible to use lighter weight non-fragmenting bullets and still have outstanding terminal performance. With fragmenting designs, a heavier bullet is ideal, as it provides more potential fragments and still allows the central core to have enough mass for adequate penetration.”





(Continue to Part 7)

[BAC]

Part 7 – Maintenance


So who here knows how to take care of their AR-15? Are you sure? Do you know what constitutes “maintenance” of the AR-15, or how much cleaning is actually needed? Would you believe me if I said the vast majority of shooters don’t?

Contrary to popular belief, the AR-15 is not a fragile weapon dependent on meticulous cleaning. It is at least as reliable and robust as the M14, to which it is so often compared, as cited by the Infantry Board in 1958, the CDEC in 1959, Aberdeen Development and Proof Services in 1960, and USMC in 1962. Over 40 years later, trainers like Pat Rogers and Mike Pannone continue to demonstrate their ARs going thousands of rounds between malfunctions, with and without cleaning and preventative maintenance.

What kinds of round counts am I talking about? Jeff, a long time police officer and SWAT officer from Colorado at 03 Design Group, had this to say in a recent (January 2010) article:



“On 12-24-09 I contacted Pat Rogers to see what the current round count of the BCM 16" Mid-Length that he has been loaning out to students. Pat refers to this BCM Mid-Length as "Filthy 14" and provided me with the following information on this gun:

Filthy #14 is the most used, and has (as 12-24-09) 28905 rounds down range. The barrel is original. It has never had a brush put through it.

-At 16,400 rounds bolt lug cracked. Replaced the bolt carrier group

-At approximately 26,000 rounds fired a 5 shot 50m group that went into 0.5". This might not be that tight at 100 meters.

-At 26,450 rds had 3 failures to extract. Replaced BCG and cleaned gun for the first time

We use only SLip2000 EWL for lube and Slip 2000 725 to clean.

**All of the rounds were fired during class (at the rate of approximately 1,250 rounds every 3 days)**

I do not recommend allowing the gun to go this long without PM (preventive maintenance). However, we wanted to see how far we could take this particular gun (#14) without being burdened by the myth of meticulous cleaning.

Keep in mind the punishment that Pat Rogers' BCM mid-length has been put through. The gun is being shot approximately 8 hours a day in a tactical training class environment at the rate of approximately 1,250 rounds every 3 days. Very few people have the time, money, or effort to run a gun like that for 28,905 rounds. This upper has the standard barrel, not the new BFH (cold hammer forged) barrel.”



Yes, that’s 29,000 rounds out of a 16”-barreled, midlength AR-15. A little less dramatic, but Mike Pannone described firing 15,000 rounds from his Noveske N4 carbine and experiencing 6 malfunctions and 3 failures to fire. In his words, "All were attributable directly to bad magazines or bad ammunition." Unlike Rogers, Pannone cleaned the rifle every 1000 to almost 4000 rounds, replaced the gas rings at 8660 rounds as preventative maintenance, and used Sprinco Machine Gunner's Lube. Heck, even the NY Times (unwittingly or intentionally) demonstrated pretty damn impressive performance from an M4 and M4A1. These reports are coming from men who see hundreds of thousands of rounds downrange per year, one of whom literally wrote the book on how to properly take care of an AR. Hearsay this is not.

Hopefully I’ve caught the interest of those who didn’t believe the AR-15 capable of such endurance. Now we’ll be a brief look at what needs to be looked at on the weapon, and how to clean it.



Cleaning

Most people will eventually succumb to the urge to clean the crap out of their weapon. On the “how-to” of rifle cleaning, I’ll defer to Chad (“borebrush” if you frequent Lightfighter), probably one of the best armorers to ever have the title; he knows a couple things about the M16 family of weapons. He is also a Marine, which means I can’t quote him word for word on this site, but I can come pretty close:

Pull the carrier. Squirt some Carbon Killer on the bolt face, and knock the <crap> off of the face.

Squirt some Carbon Killer in the chamber, turn a chamber brush a few times.

take a 20oz water bottle, pour it down the bore from the chamber. Let it drain. Pull a boresnake a few times.

Wipe off the Carbon Killer residue with a rag. Apply EWL to the bolt, reass the BCG.

visually inspect the trigger group. function check it for any breakages. If its truly <dirty>, blast out the lower with some more Carbon killer. Dump that <crap> out. Use some Dust off (hold it upright) and blow out the rest of the <crud>. Blast some EWL into the lower on the wear points.

Reass the gun. FINE. Took longer to type this <crap>.

As for cleaning the bolt:

Remove the extractor and clean the extractor recess. I do this after I've suspended the bolt in a jar of Slip Carbon Killer for 10 or 15 minutes. Means little scrubbing. While the bolt is soaking I clean the interior of the upper/chamber with Carbon Killer, chamber brush if needed, and Qtips/Rags. Change patches, QTips, and Rags as often as they get dirty. You don't wipe your <butt> with the same <crap> ticket over and over do you?

I do not waste time on the tail of the bolt, if it doesn't wipe off, it stays. Don't pick at the gas rings. Just wipe any <crud> off of them so that you can insure that they aren't missing or broken and bent.

I do get that firing pin channel clean by pipe cleaner and Slip, then blast it out with air.

While I'm cleaning that bolt I soak the carrier in the Carbon Killer. Blast it out with air, then lightly brush and wipe the thing down. Same goes for the firing pin, extractor and cam pin. Be sure to get the Cam Pin raceway clean, as carbon there can cause drag. Again, carbon there wont shut a gun down as long as it's lubed.

Once you are done with the bolt and carrier, reassemble it. ( don't leave the parts sitting around so that you can lose them.) Check your gas rings by setting the bolt carrier vertically on the bolt face. It should not fall closed under its own weight. If it doesn't, then bump the table, it should fall part way but not completely foreward. If it does, you need new gas rings.

The bore is fairly easy… if you decide to clean it. Pat Rogers and a host of other high-volume shooters rarely, if ever, clean the bores of their rifles. However, should you feel the need to, Chad suggests running a wet patch of solvent through the bore and letting it sit while you clean the rifle. As he says, “the application of uncommon sense”. Also, while you’re running patches through the bore:

DO NOT HARPOON THE CHAMBER WITH YOUR BOREBRUSH or EYELET. It is not designed to work that way. You feed the rod from the chamber end, while pulling the brush/patch through the bore. When done this way it is a one person job. If you harpoon it, you will bend <things>, break the rod, or get the whole thing stuck as the brush bends, or your patch wraps the eyelet and causes a restriction. Pull the brush a couple passes, then go to the patches. Use a patch only once. Again, <crap> tickets and your <butt>.

There. You’re done. Pretty easy, huh?

Excessive cleaning, by which I mean scrapping, scratching, etc., will do a lot more harm than good. A lot of folks complain about baked on carbon, but if you’re running the rifle wet like you’re supposed to it shouldn’t be that bad. “I wonder why my eggs keep sticking and burning to this hot dry skillet?” (Another nugget from Borebrush)



Maintenance

While you’re cleaning the rifle, you should also be doing preventative maintenance. This means checking the wear for wear parts, the checking for wear on non-wear parts, and generally looking for things that could go wrong before they actually go wrong. Shiny places are fine, but deeper wear is not. Look for fractures, cracks, burs, and similar problems.

As you visually inspect the weapon, look for symmetry.

-Do the hammer spring legs on either side of the hammer and trigger, mirror each other? Does the hammer swing true? Or is it canted or not parallel in the receiver?

-Is the gas tube parallel with the charging handle raceway?

-Does the carrier slide forward easily without any noticeable wiggle of the gas tube (without bolt installed of course).

-Is there only one lug on one side of the extractor?

-Does the Firing Pin Retaining Pin look like hammered ****?

-Are my sights canted?

Keep in mind, that like all mechanical devices there are certain items that will wear out. You will eventually need to replace the gas rings on the bolt (the procedure for determining so described above). After 5k rounds, you’ll eventually need to replace the bolt itself. The action spring will eventually compress too much (10 1/16" to 11 1/4" for carbines, 11 3/4" to 13 1/2" for rifles), and that’ll need to be replaced too. The barrel should last you many, many thousands of rounds, especially if yours is one of the barrels I mentioned earlier. When the throat finally does wear enough to consider the barrel shot-out, it’s probably about time to retire that upper.

The lower receiver assembly, barring the action spring, really shouldn’t see anything worn out. Chad/Borebrush notes that the basic fire control group in an AR-15 eats up hammer trigger pins and disconnects. Whether that means a lot to us as civilians as opposed to he as a military armorer is for you to decide. His suggestion is the Geissele SSA trigger pack. The other option is to just consider hammer trigger pins and disconnects to be wear items that will eventually need replacing. Completely your call, depending on what you want out of the rifle.



“Keep It Running”

Mr. Pat Rogers wrote an article in SWAT magazine in 2006. In it he also dispels certain myths about cleaning, as well as describes how to keep the rifle running while it’s actually being run. I strongly suggesting reading this article, which can be found online as a pdf here. Short version: run it wet, check parts for wear, run it wet, replace as preventative maintenance dictates, and run the damn rifle wet. Slip 2000 EWL, Sprinco Machine Gunner’s Lube, WD-40, even some automotive lubricants will work. Just don’t run the rifle dry and expect stellar results.




You are now armed with knowledge of how to take care of your rifle. Go forth and shoot the heck out of it.











(Continue to Part 8)

[BAC]

Part 8 – Cost/Benefit and Example Builds


Work in progress...





(Continue to Part 9)

[BAC]

Part 9 – "The Chart" and what it means


Work in progress...





(Continue to Part 10)

[BAC]

Part 10 – Further Reference Material


Work in progress...







(Safe!)

[gasmitty]

Excellent summary! Looking forward to the rest of it all. Bravo!

[RockStrongo]

Great job so far! What about the use of a sling for weapon retention as well? If you do have time to throw the sling over your shoulder, doesn't it make it more difficult to have your weapon taken from you by a bad guy? Granted.. they shouldn't be getting that close, but stuff happens..

[rottkeeper]

Nice work Bac, I've given you a gold star for your report so far.

[dukalmighty]

That there takes dedication