[AgentTikki]

Preface:

The modern consumer AR15 is an amazingly diverse system. Besides its storied history, one of its main attractions is its modular design. Almost every part of this weapons system is easily replaceable. No other platform has as much aftermarket support in the market today. It can be configured as a long range precision instrument, or a close quarters combat (CQB) pistol or short barrel rifle (SBR). It can be chambered for a wide range of calibers from the venerable .22lr to a .50 Beowulf. Early AR15s and their M16 counterparts are 20” rifles. The majority of AR15s in the commercial market today are 16” or shorter “carbines”. Extremely strong aftermarket support, and standardized parts interchangeability make this platform extremely popular with many consumers.

However, since there are so many configurations, many new consumers are overwhelmed with the choices that they face. To address this, I’ve written this document to help the first time consumer become an informed consumer. A little knowledge goes a long way to help you spend your hard-earned money. My sole wish is to provide you with enough background and general information to make a smart buy, and I will try to remain as objective as possible. I would also like to say that this is a general overview and I will not go in depth with every explanation. I do hope that after reading this, you come away with a good understanding and appreciation of the AR15.

I would also like to give thanks to my friends Dieselpower from Calguns.net, and Quentin from Firearmstalk.com for their help and suggestions. Special thanks to my good friend and cousin Connie for her time and effort in making sense of my incoherent ramblings.


A brief history:

The AR15 was developed in the 1950s by Eugene Stoner as a lightweight 5.56x45mm version of the AR10 7.62 NATO. The first AR15 was made in 1959. It was intended to be a lightweight rifle that shot a lightweight round, so that infantrymen could carry more rounds per loadout when going into battle or patrol. More historical information can be found here: http://en.wikipedia.org/wiki/AR-15


Nomenclature:

The modern day civilian market AR15 is a semi automatic firearm. The original AR15 was a select fire (automatic) weapon that was intended for military use only. Please be aware that AR15s marketed as an M4 are not truly M4s unless they have select/automatic lower receivers with automatic fire control groups, and 14.5” barrels with carbine gas systems. M16s are also select fire/automatics with 18” or longer barrels with rifle gas systems and usually a carry handle on the upper receiver. Unless you are in a state that allows NFA gun ownership, and you are willing to wade through and then wait for all the paperwork to process, you will not be able to get an authentic automatic M4 or M16. Everything else is an AR15, no matter what’s stamped on the receiver.


Figuring out which AR is the best for you.

First question you should ask yourself is: “How am I going to be using this rifle.” Your “intended use” will govern what style and what options would be more important to your choice. It should include what kind of shooting you intend to do, and at what distances. If you live in the city and can only shoot at a rifle range, you will be limited to the distances available at your range. If you want to use this gun to shoot prairie dogs at 500 yards, then your choices may be vastly different compared to the intended use for home defense. Put simply, if you want to target shoot at 1000 yards you can do it, but its not going to be the same AR as your home defense rifle.

Second question you should to ask yourself is:
“Do I buy a complete AR or make one?” This is a purely subjective question. I feel that if you are comfortable fixing a bicycle or assembling Ikea furniture, you can build at least the lower receiver by yourself,. It’s really not that difficult. You will get the added benefit of learning the inner workings on how your AR works. It is just a simple machine. There is nothing mysterious about it. Installing a barrel on the upper receiver is a bit different as it requires more specialized tools, but if you opt to build your own lower receiver and purchase a complete upper receiver you may be able save yourself some money. You will learn a lot about how your gun functions, and you will be able to choose every single component in your rifle.

Purchasing a complete rifle is a valid choice, and many people do choose to go this route. The main benefit is that you don’t have to spend any time putting it together and it comes with a manufacturer’s warranty. (Keep in mind though, if you want warranty work done on it, you most likely will have to ship your rifle in and will be without a firearm.) Competition is pretty fierce nowadays, so if you shop around you can find an AR15 complete for pretty much the same price if not cheaper than what you can build it for.

My personal recommendation is to purchase a stripped lower from a local guns store (LGS) and then purchasing parts online and looking for the best deals based on exactly what you want. I also personally try and purchase locally as much as possible. If the price difference is under 10% I will generally purchase locally. You may or may not decide to do the same but it’s nice to have a gun shop close by. Again this is my personal preference; please don’t take this as something you must do.

Choosing the right option!
The main factors that you should consider in your decisions are: need, weight and cost. To increase your happy quotient, make choices to maximize meeting your needs, while minimizing cost and weight. Remember, every choice you make, entails tradeoffs: Cost, precision, weight, reliability, utility. Keep this in mind when you making your decisions!


One important rule of thumb!
Weight is the enemy! You can hang every possible gizmo and gadget on your AR and have one blinged out, super sexy, radical tactical, ultra mall ninja 15 pound beast! Or you can have an AR that weighs just 7 pounds and does everything you need it do.


General types of AR15:

M4gery:
The most common AR15 would be the M4 type 16” barreled carbine, affectionately known by many as the M4gery. It is modeled after a standard issue military m4 carbine with the exception of a mandated 16” minimum overall length barrel and semi automatic fire controls. It can come with carry handle type upper receiver or a flat-top upper with a 1913 rail. It features a collapsible stock and a non-free floated seat of carbine length hand guards. This style is very popular, and is good for most types of shooters. Range shooting, plinking, varmint hunting, competition, home defense, and service (law enforcement/military) types all use this style. It features a carbine length gas system (7” gas tube). This is the type you most commonly see in t.v. or movies. It is what most people think of when you say M16 or M4. If you are interested in just general use/plinking under 300 yards, this is the type that is the cheapest and most readily available. With a decent barrel and decent ammunition, a good AR give you to 2-3 MOA (2-3” inch groups @ 100 yards). With a great barrel, match grade ammunition, and a good shooter, you can expect 100 yard groups easily be 1 MOA and under (one inch groups @100 yards). I would generally recommend this type of AR15 for most shooters, with an exception of the gas system. I personally prefer mid-length gas systems; I will expand on this later.


Long Range Precision / Varmint types:
If you are opting for a more specialized use that requires more precision than your average AR, this is the type of AR you should be looking at. These ARs are precision-oriented and make tradeoffs on cost and weight to achieve greater accuracy and precision. Usually the first thing that separates them from M4gerys is the barrel. In this instance, a longer barrel is chosen with different twist rates and made from different materials. Varmint types might even have slower twist rates which are optimal for shorter/lighter projectiles used for varmint hunting. The second thing that sets them apart is choice of hand guards. Precision-oriented builds will all invariably have free floated hand guards. This means the hand guards (whether tube type or railed type) do not touch the barrel throughout the entire length of the barrel. It floats around the barrel and is only attached to upper receiver or sometimes the barrel nut. Having the hand guards free floated allows your rifle to be more consistent as it protects the barrel from any pressure and movement that may change your point of impact. Beside any aesthetic preferences, hand guards can add a little weight and are usually more expensive than your average plastic hand guards. Stocks for these builds are usually bigger and adjustable to provide better check weld, stability and balance for these heavier styles.

SBR/Pistol builds:
For the sake of brevity, I’m only going to touch upon these types of AR15. Please check your local laws as to the legality of ownership of these specific models. These types are generally suited for close quarters use (less than 100 yards). I personally love these types of ARs but there are tradeoffs you must consider when purchasing them. First off is cost of ownership. SBRs (short barreled rifles) are any rifle with a overall barrel length shorter than 16 inches or has an overall length of 26 inches in length with the stock fully collapsed or folded. You must file paperwork and wait upwards of 2-4 months, and then purchase a tax stamp in order to legally own an SBR. Pistols don’t require this paperwork but may have additional restrictions that you must research in your state. This may seem a lot of hoops to jump through, but when you are done you will have a shorter lighter weapon that handles much better, and lets you track and transition much faster. There are drawbacks however. The main disadvantages are decreased muzzle velocity and increased muzzle blast (noise and flash).

Competition builds:
Since this guide is for a beginner, I will only briefly explain this type of AR. A competition model is a highly specialized AR that is designed to give any the user any advantage of speed and accuracy. They vary in length and twist to compliment what the user needs. They are usually made with a specialized trigger (light and short) and specialized optics. I usually don’t recommend this type to any first time AR owner as they are usually very expensive and very specialized.

At this point, you should have a general idea on how you plan on using your AR. I recommend that once you figure out your intended use, and then start looking for a barrel that will suit your needs.

[AgentTikki]

Barrels

Disclaimer: Again for the sake of simplicity and brevity, I will only be referring to the most common 5.56x45 NATO chamberings. Many other calibers are available for the AR but I will not get into them. I will also not get into short barreled rifles or suppressors as usually it is not a choice that most first time buyers make. Both these thing will require you checking if they are legal to own in your locale and require copious federal paperwork that will require are few months wait. I will say that SBRs and supressors are great choices, but you need to research elsewhere and decide for yourself if they are the right choice for you.

5.56 x 45 NATO VS .223 remmington.

With a 5.56 chambered barrel, you can use both .223 Remington and 5.56 nato.
With a .223 chambered barrel, you can ONLY use .223 Remington safely.
There are other hybrid chamberings available, such as the Wylde, that are found on precision type barrels that will also work with both types of ammunition. Find out what the AR you are about to purchase is chambered in first before buying it!

What Chambering Should I get?

The 5.56 x 45mm NATO chambering is a good choice for HD/SD and general purpose type shooting. It features “looser” tolerances that give improved reliability and is made to withstand higher pressures associated with the 5.56 NATO round. It is not a match grade chambering as is not a good choice for precision shooting. It is also the most common AR chambering available. For more information please refer to http://en.wikipedia.org/wiki/5.56%C3%9745mm_NATO

A .223 Remington chambered AR is not as common as the 5.56 NATO. It features a tighter chamber better suited for precision shooting. Please only use .223 ammunition with this chambering. Using a higher pressure 5.56 round may cause injury to both yourself and your rifle.

The Wylde chamber is probably the most common of the hybrid chamberings. It was originally designed as a match grade chambering that would allow the use of long 80 grain bullets. It was later found to be compatible with both .223 and 5.56 commercial ammo and found to be more accurate than a standard 5.56 chamber. It is a very good choice for a precision-oriented build or long distance shooting. There are many other hybrid chamberings all with their own unique advantages and disadvantages.


The Heart of any AR is the Barrel and Bolt.

So let’s start off by first choosing the right barrel for you. The barrel is probably the most important and most overlooked component in your AR. Most people don’t even look at the barrel; they are busy looking at the acres of rail space on the hand guards or the collapsible stock, or all the lights and lasers and optics hanging off the rails. Stop what you are doing and pick the best barrel for your intended use everything else is just icing on the cake.

Your average AR15, with a 14.5 to 16” barrel go 0-300 yards quite easily. A decent AR with a great barrel should be able to shoot 1 MOA or less in the ideal conditions (bench rested, adequate optics and optimal ammunition). Most recreational shooters can expect to be happy with 2-3 MOA (2-3 inch groups at 100 yards) with plinking ammo.


What barrel length should I go with?

So as an average consumer you must keep in mind that your total barrel length must be at least 16” inches long. The total length of your barrel and muzzle device (flash hider (FH), muzzle brake, or compensator) is used. You may purchase a 13.7” barrel and have a very long muzzle device (such as a Noveske KX3) pinned and welded to it to get it to the 16” overall length. Or you may opt for a 14.5” barrel, with a muzzle device, pinned and welded to it, to bring overall length to 16”. Most manufacturers offer 16” barrels, which do not require the muzzle device to be permanently attached (read pinned and welded). Some builders offer shorter barrels with the muzzle device already permanently attached to it.

Please be careful, some states have additional requirements as to what type of muzzle device can be used on your rifle. Please check local and state laws before you purchase. A permanently attached muzzle device may be removed by a competent gunsmith but the muzzle device may be destroyed or damaged in the process. Also there is a chance that the barrel will be damaged in the process.

As a first time buyer, I would recommend that you go with a 16” barrel (over a shorter length). This way if you decide to later on change your muzzle, it will be very easy to do. I personally like compensators, but I would recommend that you start with the basic A2 flash hider (if legal). This is because it is inexpensive and your basic 5.56 and .223 has relatively mild recoil. The 16” barrel is versatile enough to provide short and medium range capabilities. A shorter barrel would only provide a moderate decrease in weight and modestly better handling characteristics while minimally decreasing muzzle velocity.

So now that you know that you need at least a 16” overall length barrel, how long a barrel should you get? Many people assume that the longer the barrel the more accurate it will be. This is not necessarily true. Not to get overly technical, but usually a shorter barrel is more precise due to it being stiffer and less susceptible to barrel whip (with all other factors being equal). The main advantage with going with a longer barrel is muzzle velocity. The longer the barrel, the more time you have to burn all the powder and the more time your bullet gets to accelerate. The faster you get your bullet going, the faster it gets to target giving it less time to be affected by other environment factors (like gravity and wind).

For longer distances you want your bullet to be going as fast as possible so you can be as accurate as possible. Also increasing muzzle velocity increases the energy the bullet has to transfer to and incapacitate the target. Also for long distance shooting you want your bullet to be as heavy as possible with the highest BC (ballistic coefficient) so that it is resistant to changes in trajectory by wind. All things being equal, a heavier bullet loses less energy over a given distance than a comparable lighter weight bullet.

Your average M4 style 16” carbine is good for short and intermediate distances, (0-400 yards). At longer distances 300+ yards and up), the common 55 grain (gr) full metal jacket (FMJ) becomes very susceptible to shifts in point of impact due its light weight. For longer distances (400+ yards) you should consider a heavier and longer projectile, like a 69 gr, 77gr, 80 gr etc. For those bullets, a faster twist rate (1x8 1x9) is needed to stabilize the projectile. Long distance shooting is usually not for your average first time buyer. There are a lot of factors and decisions that must be made for long distance precision builds that are best left for more experienced shooters.

If you opt for a 18” or 20” barrel, you gain muzzle velocity and sight radius while trading off weight and handling. One added benefit of rifle lengths is that the gas system for rifles is noticeably smoother than shorter systems. The powder has time to burn evenly and completely. The gas produced has a lot more room to expand, and by the time it gets to the gas port it can cycle the BCG much more smoothly and evenly.

What twist rate is good for me?

The longer the projectile, the faster the twist is needed in the barrel. Nowadays, the most common rate is 1x9 (one twist per nine inches), which is optimal for stabilizing 55 grain. 1x9 means one full revolution (twist) every 9 inches. This twist will adequately stabilize and 62-69 grain bullet but may have trouble with the heavier/longer 75 grain and up bullets. I cannot be exact here because every barrel manufacturer is different, and every barrel is different. This is just a general guideline.

The second most common twist is 1x7. Most milspec barrels are 1x7 because they need to stabilize the very long tracer rounds. It will adequately handle a 55 grain projectile. And handle 80 grain bullets and everything in between. The optimal projectile is about 75 grain. It should not be used for very short projectiles i.e. 40 and 46 grain projectiles.

The third most common twist is 1x8. This is usually used by precision oriented stainless barrels. The most notable exception is S&W’s MP15, which uses this rate. My personal belief is that this is a great middle of the road rate and should be used more often. It handles the 55 grain projectiles well as well as everything up to 77 grains. You would need to test it out for yourself. It’s optimal at about the 67 grain size.

There are slower twist barrels such as 1x12 twist. These barrels are optimal for smaller projectiles, like 36 and 40 grain bullets. These are usually for varmiters that use specialized bullets for their hunting needs.

What is a CMV 4150 4140 CHF BFH HP MP CL SS barrel?
CMV Chrome Molybdenum Vanadium
4150 type a steel used in making barrels
4140 type a steel has 10% less carbon than 4150
CHF Cold Hammer Forged
BFH Barrel Forged Hammer (same as CHF)
HP / HPT high pressure tested
MP magnetic particle tested
CL chrome lined
SS stainless steel

These are different terms when describing barrel features. Honestly, for your average range gun and plinker, you do not need CL or HP MP barrels. If you only plan to shoot a couple hundred rounds a year, a CMV or 4140 barrel is more than adequate and will probably last you a lifetime.

4150 has 10% more carbon than 4140. Metal with more carbon is usually harder but trades flexibility for that hardness. It is debatable if 4150 is better than 4140. These numbers by themselves are really just stats and are not indicative of the overall quality of the barrel.

If you go through a couple thousand a year, you might want to invest in CL barrels as they will last 3-5x longer. Chrome lining will slightly decrease precision of your barrel, but it is a very small loss. It will also cost a little more, but your barrel will last a lot longer and be a little easier to clean.

An alternative to chrome lining is ferritic nitrocarburizing (FNC) aka Tennifer and Melonite. So far I am only aware of S&W and LWRC using this process on AR barrels. This process treats the surface of the barrel itself, unlike chroming. It is a case hardening process that infuses carbon and nitrogen into the metal itself. My tests have shown that FNC creates a surface that is harder than chrome and resists corrosion better too. FNC has a great track record with pistols as is the case with Glock’s legendary Tennifer finish. It remains to be seen if it can handle the higher velocities and pressures associated with rifle rounds.

Besides cost, chrome’s only downside is that it applies to the surface. Since it is nearly impossible to lay down a completely even layer of chrome, chrome-lined barrels are usually not as precise as they were before chroming. This is not to say that chrome lining a barrel will make it inaccurate. If you take a stellar barrel and chrome it, it will still be a stellar barrel. It will be just a little less precise and a whole lot more durable. Conversely, if you take a crappy barrel and chrome line it, you now have a crappy barrel that will stay with you forever.

There are two main downsides to FNC. First, since it is relatively new, and although it was tried and tested in pistol caliber barrels, it doesn’t have long history or track record with the higher velocities and pressures associated with rifle calibers. Second, FNC is a highly toxic process. This means it is harder to set up and maintain the equipment required for this process. So facilities that offer this service are uncommon.

Many people are saying that FNC is the wave of the future and that FNC will replace chrome in a few years. I believe that it looks very promising, but only time will tell if it will be a viable option.

If you need a service type weapon or want a dead nuts reliable weapon for SD/HD purposes, you will want to invest in a barrel that is HP AND MP tested. HP and MP testing is added insurance. It will greatly reduce the chance your barrel will be rendered inoperable by voids and inclusions undetectably by the naked eye.

CHF and BFH describe a manufacturing process that produces a great service type barrel. Please note, CHF is not optimal for precision type builds. The CHF process makes a very strong durable barrel. I personally think that it is worth the additional cost, but I don’t see it necessary for a plinker or light use weapon.

Stainless Steel (SS) barrels are usually found in precision type barrels. SS trades off wear and corrosion resistance for more precision and accuracy compared to CL and harder steel barrels. They also tend to erode faster and will not last as long as other types of barrels.

Please keep in mind that all barrels wear out due to usage. While a CL barrel might last longer, by 40k rounds, it’s not as precise as it was when it was new. Precision barrels might only last 10k rounds but some shooters might ditch it by 4k rounds because their needs are no longer being met due to wear and erosion. Also overheating your barrel will wear it out faster. If you like to dump mag after mag of ammo, your barrel will wear out faster than if you slow fired the same number of rounds.

One very important thing to remember about barrels, please don’t think that every CHF barrel or 4150 or SS barrel is the same. Different barrel makers will have different recipes for steel even if they are all considered 4150 or CMV or 4140 etc. There are different ways to rifle and chrome barrels. There are different ways to measure headspace and to do quality control inspections. What you are paying for is all the expertise, craftsmanship, and quality control that a particular barrel maker utilizes when making your barrel. Please remember the old adage: You get what you pay for.


Barrel contours:
The three main types of contours are LW light weight, Med Con medium contour, and Heavy (Bull barrel / Hbar). The stiffer the barrel, the more accurate/precise it tends to be. Heavy contours are best utilized for bench rest shooting or fire suppression roles. They soak up a lot more heat, so you can get more rounds through it before groups start to open up or the barrel overheats. On the downside, they take longer to cool down and they are heavy to carry and hold steady while shooting free hand. Interesting note, heavy contours are cheaper to make than other contours. This is because other contours take more machining time to pare down or shape from the blanks that they are made from.

Medium contours like the M4 contour are probably the most widely available. The M4 style has a cutout in its profile that is there to allow you to mount a grenade launcher. Unfortunately, the average consumer is not allowed to have destructive devices, like a grenade launcher, for example. The M4 contour is a little lighter than other medium contour types. There are many other kinds of medium contours and are arguably the most popular, as they provide a good balance between rigidity and weight in relation to either extremes.

LW builds (my personal favorite) make great service type carbines. They are easy to handle, carry and shoot. But they will show their downsides if you are ever in an extended firefight (or just doing multiple mag dumps). Also, they are not the best choice for precision builds due to relative flexibility. If you are building a range/plinker, a LW or medium contour is just right for you.

Special note to all builders, please take note of the diameter of the barrel around the gas port. You will need to match your gas block to this measurement.


Barrel Extension
The majority of barrels made for AR15s have the extensions already on them. The extension is located on the end opposite of the muzzle that goes into the upper receiver. It is affixed to the receiver with the barrel nut and houses the chamber. High round count barrels will exhibit throat erosion, which can lead to dangerous shooting conditions. When buying a used barrel or upper, it’s always a good idea to use a headspace gauge or have a professional check it out. Go/ no go gauges are relatively cheap and are a good addition to your specialized tools inventory. Also chrome-lined chambers are usually more desirable as they are easier to clean out and more durable than standard parkerized versions.


Feed Ramps:

My personal take on this is that, since M4 feedramps cost the same as non M4 type, why not get them. It is debatable whether or not they will make your AR feed more reliably. As a general rule of thumb, make sure you match your upper receiver type to the ramp type of your barrel extension. So match non M4 to non M4 and M4 feedramps to M4 feedramps. While you can get away with M4 ramps on your barrel extension and non M4 upper, you won’t be able to get away with using M4 feedramp type upper and non m4 feedramps on your extension. This combo M4 feedramped upper with Non M4 ramped extension will give you failure to feed problems.

There is some debate on M4 ramps. One valid argument advocates only using upper receivers without feedramp extensions. This gives the benefit of being able to use regular rifle ramps and m4 ramped barrel extensions. If you plan on changing barrels often, this may be a viable option for you. This is a valid argument especially if you plan on changing barrels. There have been reports of people running into issues with their receiver ramps not lining up with the ramps on the extension of their new barrels.

Bolts and BCGs

The bolt is housed within the bolt carrier assembly (BCG). These are the parts that cycle back and forth within the upper receiver every time your fire your AR. When you pull the charging back, you are essentially pulling the BCG back and out of battery. When you release the charging handle, the BCG springs forward over the magazine well, picks up a new round, and puts the round into the chamber. The bolt holds the round in place ready for you to pull the trigger, which releases the hammer. The hammer strikes the back of the firing pin pushing it through the bolt to strike the primer on the round thereby firing it. The bolt is subjected to the highest amount of stress in your AR.

Get a good bolt. Don’t choose the cheapest option. If your bolt breaks, your gun goes down. Bolts are subjected to the highest amount of stress in your AR. Carpenter 158 steel is mil-spec should be considered minimal for any service level grade AR. Bolts are relatively cheap. It is only $50 for a good one. Please don’t skimp on this part. MP/HP testing should be a requirement for everyone’s build. Chromed or coated bolts and BCGs are nice but not necessarily needed. Coated units definitely make cleaning easier, but won’t necessarily make your bolt any more reliable than it already is. A regular parkerized bolt will do the job just fine. I would also recommend that you get a spare bolt, extractor, extractor spring and firing pin in your bag of tricks.

BCG (bolt carrier group) is the term for the whole assembly which includes the firing pin, bolt, and housing. The carrier usually doesn’t wear out and can be reused. When deciding between a semi auto (SA) and full auto (FA) carrier for semi automatic applications, either one will do the job. FA carriers are made heavier because more mass is needed to slow the cycling rate of full auto applications. Heavier does not necessarily mean better in this instance though. Most FA carriers also have a small shroud that protects the firing pin from hitting the hammer when the BCG cycles back and cocks the hammer. For SA guns, this difference is negligible and in some cases unwanted. There are applications (mostly for competition guns) where some users actually want the fastest cycling possible and opt for light weight BCGs. My personal opinion is that since most factory guns are overgassed, I would prefer a full auto carrier for the added mass and for the shroud protecting the firing pin. Interestingly enough, having a FA carrier doesn’t make your gun automatic nor is it really necessary for all FA guns.

Insist that the gas key bolts of your BCG are properly staked. It’s added insurance to keep your gas key secure, thusly preventing any stoppages. Some manufacturers insist that staking is not needed (i.e. Young’s) but it’s really not too difficult to do yourself if needed.

[AgentTikki]

Gas Systems.

There are 2 major types of gas systems that the AR runs on. The first being DI (direct impingement) and the second being piston. DI is the original design. Piston is a relatively new development. There have been forays into piston designs in the past, but it’s only been recently that piston driven ARs have been become popular. The best thing I can do you is show you the pros and cons a piston system offers, it’s your personal choice to decide if it fits your needs. Please understand that since there is no set standard for a piston system, every piston system is a proprietary design that will require different and non interchangeable parts.

Pros:
*A cleaner running system. (less fouling of the BCG and chamber, more fouling by the gas block or exhaust)
*Should be more reliable in adverse shooting environments.
*Should be easier to clean, (provided you don’t need to remove the hand guards)

Cons:
*Costs more than a comparable DI setup
*Weighs more than a comparable DI setup
*Harsher recoil impulse (I concede that this is subjective and debatable)
*Inherently less accurate,(minor)
*Slower follow up shots (minor)
*Proprietary parts make it harder, costlier, and longer to replace broken parts.

Personally, I would only recommend a piston setup if you where looking for a non precision type carbine and need the extra reliability due to your expected shooting environment.

DI gas systems come in 4 flavors: Rifle, mid-length (middy), carbine, and pistol. The most common types are carbines, with 7” handguards. The next most common types are rifles with 12” of rail. Relatively new developments are midlengths with 9” handguards. Pistols are uncommon and I won’t be going too much into them. Only consider rifle length gas systems for 18+ inch barrels. Both carbine and midlength gas systems can be used for 14” to 16” length barrels. For these lengths, I usually recommend midlengths as their advantages outweigh their disadvantages:

*Weight: Advantage Carbines. Since the midlength rail/hand guard and gas tube is 2´ longer, it weighs more, not much more, but carbine gassers are clearly lighter.

*Sight Radius: Advantage Middy. Being able to put the front sight 2” farther from the rear sight is a clear advantage. The longer the better.

*Longer hand guard rail: Advantage Middy. I admit this is a subjective point, but unless you have freakishly short arms, the carbine length guards are going to be really short for you. Even my 5”1” wife likes the length of the mid length over the carbine.

*Aesthetics: Advantage Middy. Again purely subjective, and you may disagree with me on this point, but to me a carbine looks unbalanced with the exposed barrel being too long.

People point out that since the gas port is so much farther away from the chamber and gas pressure should be lower, middies should be inherently smoother and easier on all the reciprocating parts of your carbine. While I agree with this in theory, I’ve personally found that most middies are overgassed. So this makes the whole “less recoil, smoother impulse” debate a moot point. Most builders overgass systems in order to cycle the cheap under powered target and plinking ammo. I’ve personally shot a few middies that were over gassed and recoiled harder than carbines, and vice versa. This is dependant on how the gas port is sized. As a consumer, you really don’t have any control over the gas port sizing of your barrel or have any way to check or measure it, unless you order a custom barrel for your build. Also since it’s better to have a slightly overgassed system (feed all power levels of ammo) as opposed to an undergassed system (only feeds higher powered ammo), I will call it a draw.

So in my humble opinion, for the minor inconvenience of a few extra ounces of weight, you get a lot more in return with midlengths. Costs are about the same for either option some builders charging a little more for middies.

Please understand that once a gas port is drilled into the barrel, it is very difficult and expensive to change from a carbine to a middy or vice versa. If you have a carbine gas system, don’t worry too much. If you want a longer rail or hand guard, it is relatively easy to swap out the gas block to a low profile model or modify a front sight base.This allows you to free float a longer rail or hand guard over it. The same can also be done on midlengths and rifle gas systems if you want an even longer rail.


Triggers

For someone just starting out with an AR, I would really recommend that you just get started with a standard mil-Spec type trigger. There are a myriad of choices out there from 2 stage to fast single stage competition types to fully adjustable models for long range competition. To me a good mil-spec type trigger is good for shots up to 200 yards. Beyond that, I feel the need for a more refined trigger and look for 2 stage triggers. I’ve shot with shooters that do amazing things with a standard trigger all the way to 400 yards, but for me I like a good two stage for those distances. If you are going for a precision build or looking to shoot tiny, tiny groups, a light 2 stage trigger has many advantages. First and foremost being the 2nd stage. It allows you to know exactly when and where the trigger will break. Some shooters will prefer a single stage, but most use 2 stagers for precision work. One thing most people don’t know is that a 2 stage trigger will feel just like a single stage if you pull it hard and fast. For close quarter or speed shooting, 2 stagers feels just like a standard single stage trigger.

If you are not sure exactly what you want, just stick with the standard mil-spec trigger. Once you get a lot of trigger time under your belt, you can then re-evaluate your needs. Most people will find that the standard trigger works for them. Some will find that they need something more. As a first timer, don’t upgrade until you’ve got a good reason too, and don’t rush out to put in an expensive aftermarket trigger your first time out. If you can become proficient with a standard mil-spec trigger, you will be a better shooter overall. Also if you train on a standard trigger, it would be easy to pickup any standard AR and shoot well with it too.


Accessorizing, pistol grips, stocks, slings, magazines.

As a first time buyer, I would really recommend you getting just the basics your first time out. Get you hands on your AR, some good magazines, and lots of ammo, and then go shoot it. Shoot it a lot. Have a lot of fun with it. Learn to use your iron sights. Learn the ergonomics.

After a little range time, figure out what you need and what you want, and then upgrade it. One of the biggest mistakes that I’ve personally made, is that I bought a lot of upgrades for my AR all at once. I eventually decided that I didn’t want or need most of them and changed them back. In hindsight, I just should have upgraded slowly piece by piece, one range trip at a time until I found exactly what I wanted. All I would recommend is a nice sling, plenty of magazines and ammo, and a shooting buddy or two. Aftermarket triggers, optics, lights, and lasers all have their place, but when starting out, please just take it slow. Learn the basics on your AR. Understand how to use the irons sights and manipulate the ergonomics. Then make changes to suit your personal needs and tastes.

I could easily write a 300+ page book on all the different type of accessories, but honestly the market is constant evolving and this primer would become dated quickly. Just remember to balance your wants and needs, with weight, cost, and utility.


The age old question:

Why isn’t X,Y Z brand good enough, and why are they so much cheaper than this Colt, BCM, LMT, or Daniel Defense (etcetera)?
What you are paying for is intangible, and mostly invisible. You are paying for quality. These brands are what I would consider service grade ARs. These are guns that satisfy my minimum requirements for overall quality for a work gun. I am paying for higher quality components, testing of materials used, and tighter quality controls. I am paying for a company with a track record of NOT cutting corners and experience building quality rifles. For a range gun, I would like 100% reliability but, when I’m in a gun fight, I demand 100%.That being said, nothing is 100% perfect. But at least with these builders/manufacturers they are much less likely to fail when put to hard use. I am not saying that your Vulcan, Blackthorne, Stag, DPMS, Delton, Olympic, Bushmaster, Spike’s, PSA is an unreliable POS. I am saying that Colt / BCM / DD are less likely to have a stoppage.

That being said, if I had Brand XXXXXX, that I plan to use for work, or HD/SD, I would put at least 1000 rounds through it first. I would test it out with a variety of different types of ammo and test out all my magazines. I need to ensure that positively, definitively my AR is reliable and good to go, no matter what make or model I have.


Now that you know a thing or two:

Expect that most lower priced, brand new ARs will start at about $600. Service grade ARs are a bit more starting around the $1000 mark. If you have the time and patience, search the equipment exchanges on various gun boards, wait for sales, get into a group buy or two, and buy your AR one piece at a time. If you aren’t adverse to buying used parts you can save even more. I would not recommend buying a used lower parts kit since they are cheap new. Just suck it up and buy a new one. Delton, DPMS, Olympic, Bushmaster, Spike’s, Palmetto State Armory all make decent quality ARs. From my past research but no personal experience, I would stay away from Vulcan and Blackthorne. I would also shy away from small boutique brands that no one has ever heard of. Remember Google is your friend, use it. Research any complaints with any particular brand or model you are interested in, and also do a quick search of that brand’s warranty and customer service. Do take your time. Do your own research, Do not buy on impulse. Pick a few models that appeal to you and post up your questions and ask for opinions. You will find many helpful people out there that will steer you in the right direction!

Hope you found this guide informative, I welcome any comments and criticisms that you may have.

[ZombieKiller83]

Solid write-up Tikki, very informative, i vote sticky

[Quentin]

AgentTikki, that is excellent and certainly deserves to be a sticky! Thank you for going to so much trouble on this AR Primer. The information is excellent and spot on - you say just enough and don't drone on, just the facts and enough explanation but no drivel!

I like the way you jump right in at the beginning with the most important topics then keep expanding into other areas a new buyer should be researching. By the end you've touched on all the important areas and I feel that anyone following along should have a much clearer idea of what they need to choose before buying. Your writing style is clear and nonconfrontational, people who want to buy a Colt or even a DPMS will come away learning something yet not angry that their brand was disrespected. And the Nazi in me approves of your grammar and writing!

Bravo! This is an important tool for the new buyer and many others including myself. It's also nice to have all this information pulled together in one concise up-to-date document.

[mjkeat]

Good post Agent.

[ShagNasty1001]

Wish I had this when I was buying my first AR. Very good post

[AgentTikki]

Thank you for all the kind words!

Took me a while to proof, (even if I had a lot of help!)

Sorry I couldn't get it out earlier ShagNasty1001!

[ar15noob]

Agent You Rock...as you can tell from my name this is coming in VERY handy...along with the others who respond to my mundane posts

[SouthernSwag]

Are flip up sights worth the money...I just got an ar and was thinkin bout going ahead and getting them...my rifle is pretty much multipurpose...sport/home defense/end of the world and I plan on getting an eotech holo