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This is a post from the M4 Carbine website, but I think it would be very beneficial to have here as well as there seems to be alot of members unfamilar with the vast array of m4 type ARs on the market. The gentlemen who wrote this, Rob, is a SME and his thoughts and advice are well heeded. At the end of the post is a link to the chart that is referenced; and don't worry, if you do own an AR with fewer X's, with just a few "adjustments" you can have a quality AR. I own a BM and a Colt and with a little work the Bushy became just as dependable.
Enjoy.
Now I'm an AR15 owner, now what?
by: Rob_S at m4carbine.net
Well welcome to the world of the evil black rifle!
Hello my name is Robb I'm also known as 'gotm4' on many gun forums.. I’ve been into ARs since the early age of 5 in 1975 after shooting a M16 with my dad (an active duty US Marine at the time, now retired).
Anyway since that day I’ve been a gun nut meaning I tried to learn everything about guns. While living at Quantico I assembled my first AR in 1987 with the help of my dad's armorer. At the time my dad worked at Firepower Division at Quantico MCCDC. Firepower Division along with Weapons Training Battalion is where the M16A2 and XM4 really came into existence. I remember seeing prototypes of both there. I visited my dad at work usually a few days a week. I got to hang out in the armory and see how the rifles and carbines were repaired, cleaned and got to shoot a lot of these guns. That is where I met LtCol Dave Lutz USMCR (now a Knights Armament employee) and Maj Jack Muth III (now a retired Colt Defense employee) my dad worked under both from 1986-1991. This is also where I met SSGT Andy Guthrie (deceased) and SSGT Owens. Owens helped me assemble my first AR. For my first ‘build’ I used a cast Essential Arms lower receiver and several parts from Quality Parts (which later became Bushmaster). I assembled a 20” HBAR using a 1x9 twist blackened stainless steel barrel. It was a very accurate rifle and I had a lot of fun with it.
Well enough about me.
With the mad rush to buy so-called 'assault weapons' due to the incoming president-elect, who has said he wants to bring back the 1994 Assault Weapons Ban and make it permanent. Because of this fear anything AR related is very hard to get right now. Some people think that on Jan 21st 2009 Obama will ban ARs, AKs etc. People are panic buying mags and ammo. Sales are up about 60% in the gun store where I work.
Lets talk a little about what you may have bought, what you didn’t buy or what you might want to buy. You may have bought a complete gun or you may have bought a complete upper and lower slapped them together, or you may have built up your AR from parts. All AR parts are not created equal.
You might be familiar with ‘The Chart’ put together by Rob Sloyer aka 'rob_s'. I wrote this article to help understand the data contained within ‘The Chart’ and to help a new AR owner figure out what to do to get the most out of their new AR15. The chart is a great resource of what to look for in an AR but those people unfamiliar with ARs might not understand it's content, and to them it might just look kind of like The Periodic Table of Elements. The Chart can be confusing to people who don't understand the things that are listed. I've written this article to help inform the new AR owner as to why he/she might want some of a particular AR features in it's columns, or why something is ‘mil-spec’.
My new AR doesn't have many Xs in The Chart, is it not 'mil-spec'?
Are 'mil-spec' features always desirable? It depends. Some things are not 'mil-spec' and would serve you just fine. For 14.5” to 16” barrels I prefer midlength gas systems. This is because they shoot softer and have less parts wear. However 'mil-spec' for and 14.5” M4 barrels is carbine length gas systems. I like LMT enhanced1 bolts for SBRs because they last longer than standard bolts. However the 'mil-spec' for bolts is the standard MPI and HP tested bolts as used in the M16-A1/A2/A3/A4, the M4 and the Mk18. 'Mil-spec' doesn't always mean the best available, it's just means that the military wants a known quality for it's equipment, in other words a baseline.
Another example: 'mil-spec' barrels for M-16s and M4s are chrome-lined and typically made from 4150 steel, do you need this? Maybe or maybe not. If you’re a Hi-power service rifle shooter or a varmint hunter and you’re really more worried about absolute accuracy. You're not worried about how long in tens of thousands of rounds this barrel will last you while maintaining 4MOA, many Hi-power service rifle shooters change barrels every 1-2K rounds and the vast majority are stainless or chrome moly steel. If you're wanting a plinker, a defensive rifle or a training carbine for classes you'll likely want a chrome lined barrel. Can chrome lined barrels be as accurate as stainless barrels? Sure they can, FN has proved this with their fantastic SPR bolt action rifles which typically shoot under 1 MOA. However the vast majority of chrome lined barrels aren’t made in the same way as FN does their bolt action rifle barrels. Typically if a shooter wants the best accuracy out of a barrel he/she will buy a stainless or chrome moly (non chrome-lined) barrel. Most chrome-lined AR barrels shoot between 1-4MOA depending on how the guns is setup. This is perfectly fine for carbines as most people are either using irons sights, Aimpoints or EOTechs. Aimpoints are typically 2-4MOA and probably 99% of AR shooters can't shoot 2MOA with an Aimpoint at 100yds anyway. I can shoot with iron sights better than I can with red dot sights, but red dot sights make me much faster which is why I use them.
Why is chrome lining used in military barrels?
Chrome lined barrels last longer than almost all other known barrels, typically last twice as long as stainless non-chrome lined barrels. Chrome lined barrels are easier to clean than most other barrels. Chrome lined barrels are much more resistant to corrosion from shooting corrosive ammo and or rusting etc.
As a whole, quite often a chrome lined barrel is less accurate than a comparable stainless or non-chrome lined chrome moly barrel. Sure some chrome lined barrels are very accurate. I have a friend that has a 20” chrome lined 1x7 twist barrel which shoots 50gr JHP American Eagle factory loads into a ½” at 100yds. It proves that chrome lined barrels can be accurate and that 1x7 twist doesn’t somehow ‘over stabilize’ light weight bullets as many people believe.
About the caliber:
Do you have or want an AR chambered in 5.56mm NATO or .223 Remington?
Do you have or want something more rare like a 5.45x39mm, 6.8SPC or 6.5Grendel?
Or do you have something which is neither something like a .223 Wylde or 5.56 Noveske Match Mod 0 chamber?
Mostly I'll be talking about .223/5.56mm NATO. The other calibers are newer to the AR and the vast majority of people aren't shooting those in the same quantities as they are .223/5.56mm
When speaking about calibers people use .223 and 5.56mm interchangeably. Just like some use 'clip' and 'magazine' and they are also not the same. Sometimes things are even more confusing with ARs. On some of their ARs Colt marks their lower receivers as .223 but then 5.56mm NATO on their barrels. Colts are chambered in 5.56mm NATO. This is okay since you can shoot .223 Remington in a 5.56mm NATO chambered barrel with no problems.
Max chamber pressure for 5.56mm NATO spec is 62,366 psi.
Max chamber pressure for .223 Remington SAAMI spec is 55,000 psi
5.56mm NATO, .223 Wylde and Noveske chambers can handle the high pressure levels of 5.56mm NATO ammo just fine. The 5.56 Noveske Match Mod 0 chamber is similar to the .223 Wylde chamber but is better suited for full auto use versus the .223 Wylde.
SAAMI spec .223 Remington chambers can be dangerous if 5.56mm NATO ammo is used in them, especially in older guns. Typically, in ARs it isn't dangerous, but .223 Remington chambers usually won't don't run well at all with 5.56mm NATO pressure ammo. The rifles will typically have failures to extract, blown primers, which will sometimes lock up the gun or make it not be able to fire. Sometimes that primer that's been blown out of the casing ends up under the trigger in the lower receiver and can keep the trigger from camming down when the shooter pulls the trigger to fire the rifle and the rifle won't fire, I've seen worse where it gets stuck up between the bolt and barrel extension which was quite hard to get it cleared and safe to fire again.
Why would someone want a .223 Remington chamber?
Because a .223 Rem SAAMI chamber is very accurate with the lower pressure SAAMI pressure .223 Remington ammo. The only guns that my wife and I have that don't have 5.56mm NATO chambers is her Noveske gun (556 Noveske Match Mod 0 chamber polygonal 1x7 twist) and our 3gun rifles. Our 3gun rifles have stainless 18” SPR profile White Oak 1x7 twist w/M4 ramps and. 223 Wylde chamber barrels.
Generally speaking for the most reliable defensive use AR, the barrel should be chambered in 5.56mm NATO, Noveske or .223 Wylde. .223 Remington has shorter lead. (The lead is the distance the projectile of a chambered round must travel upon ignition before it enters the bore of a barrel. It is measured in thousandths of an inch and is a datum of considerable interest to benchrest shooters). If 5.56mm NATO pressure ammo is fired in the .223 Remington chamber it can cause damage or failures in the rifle. The short lead drives the chamber pressure very high. Some AR barrel manufacturers have very tight .223 Remington type chambers. This is fine if all you'll ever shoot through those guns is .223 Remington SAAMI spec ammo. If you have a barrel that isn't a Noveske barrel and isn't chrome lined with 1x7 twist and doesn't have M4 feed ramps, be very suspicious if someone is telling you it's a 5.56mm NATO chamber. 5.56mm NATO, .223 Wylde and Noveske chambered guns can run with .223 Remington ammo and won't have any problems. It's like using 93 octane in a car that only requires 87 octane, it doesn't really hurt anything but do it the other way around and it could cause problems.
Things to consider if you're reading this and haven't yet bought your AR:
What is your ARs purpose?
Is it for use at training courses?
Is this AR for competition? 3gun or Hi-power? (They differ greatly)
Does your rifle have a dual purpose role?
Do you just want an AR as something to show off during the holidays or because you think ARs will be banned?
What length barrel do you want?
Do you want a carbine (less than 18” barrel?)
Do you want a full size or bigger rifle?
What length gas system do you want? (pistol, carbine, midlength, intermediate, rifle)
How many rounds per month/week/year will you shoot?
How much do you want to spend?
Most AR owners shoot no more than about 1K rounds per year with the vast majority shooting one eighth to one half of that. If that's all you'll shoot, you probably don't need to worry much about anything other than buying decent ammo and magazines and a 1 oz bottle of oil.
For the last 4yrs shooting competitively, training and recreational shooting I average 12-20K rounds per year depending on how many multi-gun/3gun matches and training courses I attend per year. My goal for training is to take at least one carbine/pistol class per year. My wife averages 1-2K rounds per year. My wife and I own 7 functional ARs and have two other lowers that aren't built into rifles. So you can see even with the large amount of shooting that I do, the amount of rounds is spread out among the different rifles. The rifles/carbines I shoot the most currently are my 3gun rifle, 10" SBR, Colt w/PWS piston conversion, in that order. Even with as much shooting as I do, I don't get wrapped around the axle about the barrel steel etc. as some folks do. Sure some are better than others, my 12.5” SBR it's a 1x9 twist cut down from a 14.5” Bushmaster barrel. I 'shaved' the front sight base down so it fits under the Daniel Defense RIS II Mk18 rail. With 55gr ammo, this barrel with my suppressor is more accurate than my LMT 10” SBR. Is my Bushy 12.5” barrel as high quality as a Colt barrel? No, but for me it gets the job done. Depending on what you are doing with an AR, you really have to know your priorities.
If your AR is used for training/personal defense or is a jack of all trades rifle and you'll shoot more than 1K rounds per year I would highly suggest a chrome lined barrel. I would also suggest the following:
Use a MPI and HP tested bolt (if replacing yours I'd suggest a BCM or LMT bolt).
Ensure the carrier key is torqued and staked sufficiently.
If your carbine has a collapsible stock I would suggest having the castle nut end plate staked into the castle nut.
Make sure your ejector and extractor are of high quality and have the correct extractor spring and black extractor spring buffer installed with it. If you're using a Colt, LMT or BCM bolt you'll already have top quality parts. In ARs with carbine length gas systems you should run a black extractor spring buffer and a 5-coil extractor spring. If you have an AR with a midlength or rifle length gas system, it will work with a blue or black extractor spring buffer and the smaller extractor springs. I use the 5-coil ones in all my ARs that have standard type (non-LMT enhanced) bolts regardless of barrel/gas system length.
All of these things are done on 'tier 1' ARs. Tier 1 basically meaning a Colt or FN. Both are truly Tier 1 'mil-spec' guns because the US Military uses both. FNs aren't available to the public so we really have to rule them out. The next closest brand is LMT.
Will another brand of AR other than a Colt or LMT serve you well?
Sure. Especially if you fall into that 1K rounds or less per year category.
Example, lets say all you can find is brand X, Y or Z, and you just got it because that's all you could find and you want this as reliable as possible because you'll use this gun for training classes or self defense. Lets say the rifle doesn't have as many Xs as does a Colt or LMT rifle in The Chart.
Things I would do or check on non-Colt or non-LMT brands:
If the carbine you bought doesn't have a HP and MPI tested bolt I'd buy a BCM or LMT bolt, firing pin, cam pin and use them and keep the factory bolt, firing pin and cam pin as spares. If you ever take a carbine class, you should have these parts as spares anyway. If you bought a rifle length AR, the bolt is a little less of a concern. 20” guns have the best reliability of all ARs. Bolt life is the longest on the 20” or longer rifles. You should still make sure that you have a good cam pin, firing pin, extractor and ejector and springs for each. An easy way to make sure you're getting good parts like this is from BCM, they offer a SOPMOD bolt upgrade kit which includes a proper 5 coil extractor spring, black ex. spring buffer, a Crane O-ring, a extractor pin and a set of gas rings. Don't use Crane o-rings on anything with a gas system longer than carbine length, it can cause feeding problems on slower running guns. Then take the AR out and shoot it, if it'll run for more than 500 rounds without any stoppages then you're good to go.
Your spares kit should have the above plus a spare buffer spring, a hammer, trigger and disconnector and their springs. A spare bolt catch kit, mag catch kit, at least two take down pin detents and springs as well a selector detent and spring.
On the other brands of unknown quality (few Xs on The Chart) I'd either replace the carrier key with a BCM, LMT or Colt carrier key along with new carrier key screws or at a very minimum remove the factory carrier key, degrease it, lap the bottom of it, this means using a whetstone to remove the finish on the bottom of the key to ensure it's absolutely flat and not warped and will now seal well against the bolt carrier. Apply red loc-tite or better yet Rocksett to the bottom of the carrier key, reassemble and torque the carrier key screws to 50-55in lbs (higher than the USMC technical manual I know). Stake either with a chisel and hammer or best with a Ned Christiansen MOACKS tool. Staking is pushing some of the carrier key metal into the screw heads to keep the screws from loosening due to heat and vibration. If you test fire the gun a few hundred rounds of high quality preferably NATO pressure ammo and even with the above improvements it still doesn't run well, I'd ream the chamber with Ned Christiansen 5.56mm NATO neck and throat reamer. If the rifle has a lot of Xs in the chart in all likelihood you have the correct size gas port for 5.56mm NATO pressure ammo. If it has fewer Xs in the columns of The Chart, more than likely you should replace a CAR buffer with a H or H2 buffer if you're going to be shooting 5.56mm NATO pressure ammo. The lower end ARs use larger gas ports for people who buy weaker .223 Rem pressure ammo.
CAR buffers are 3oz
H buffers are 3.8oz
H2 buffers are 4.6oz
H3 buffers are 5.6oz
Now that you're a new AR owner, are you also going to jump into NFA?
Meaning do you want to register your AR as a short barreled rifle (SBR), buy a sound suppressor or buy a registered full auto lower?
If so you will definitely want to ensure that your AR is up to the task. As above, you should be using a MPI and HP tested bolt with top quality ejector and extractors. Depending on your barrel length and brand of barrel, you should use a H to H3 buffer with your AR if running a sound suppressor.
SBRs are harder on everything vs. a 16" carbine. 16" guns cycle faster than 20" guns, and SBRs cycle faster still. Why is this? This is because the original AR was a 20" rifle length gas. Carbine length gas ARs are running almost double the gas pressure of a 20" rifle gas gun. This shorter gas system adds much more pressure and heat to the bolt and the bolt velocity is faster the shorter you go with the barrel. Bolt life is shorter and other components wear out faster in the shorter guns. It's almost unheard of to hear of a 20" AR using a MPI and HP bolt to break a bolt. Carbine length ARs will break bolts from 3K to 20K rounds depending on you're firing schedule. It gets worst the shorter you go under 16". 10" guns wear things at a rapid pace and even worse if you use a sound suppressor.
Sound suppressors add even more gas pressure to the already fast cycling high pressure short gas system. Example, if running suppressed my 10" will wear out a set of gas rings in about 1K rounds. If I shoot it unsuppressed I can easily get 2K rounds out of the rings. Cam pins if running suppressed look beat to hell in about 1.5K rounds, if unsuppressed 3K rounds. Because of this added wear, I use a LMT enhanced bolt which has relieved bolt lugs and and upgraded extractor which has dual extractor springs. This gun has only ever had a stoppage twice (I don't like the word 'jam'. Jam is what you put on biscuits). Both stoppages were due to shooting Radway Green ammo when I didn't have the suppressor mounted. Both stoppages were failures to eject because the gun short cycled. Short cycles are where the bolt carrier doesn't move far enough rearward in its travel to eject and/or pick up the next round in the magazine to feed. Radway Green ammo has a pressure spike that drops very quickly (Radway Green is made for the British SA80A2) and won't work in most of my ARs unless I'm running them with the sound suppressor. This ammo does work in my piston Colt/PWS AR as well as my Arsenal SLR-106FR (5.56mm AK).
If your AR is for competition, varmint hunting you can really set it up any which way you want.
If your AR is just for showing off, or you just bought it because you think they might be banned and you aren't actually going to shoot it then don't change a thing. Do what you want since it isn't a life saving tool.
Piston ARs:
If you are planning to build or buy a SBR or full auto or use a sound suppressor, I would suggest considering a piston gun.
Many people think they need a piston AR or they need to convert their standard AR to piston. Many of these people use the excuse that piston ARs run better than direct impingement ARs or run cleaner. This is not the case. Piston guns have their own sets of known problems. These are just different problems and weakness areas vs. standard direct impingement ARs.
Piston guns get dirty as well just not at the bolt, bolt carrier and in the upper receiver, piston ARs are more forgiving of the lack of lubrication (because the bolt and carrier aren't getting as hot and hot gas isn't blown into the action), they can be run with a little less lubrication than direct impingement ARs. I have the Primary Weapons carbine length piston conversion on my Colt 6920 upper. It gets plenty dirty. After a thousand rounds or so it looks like I've airbrushed carbon all over the gas block and the rail and barrel near the gas block. This is where it bleeds off the excess gas not used to cycle the bolt. If shooting without a glove on my left hand it gets very hot in this area pretty quickly, actually hotter than comparable direct impingement ARs.
Many piston ARs suffer from bolt tilt. Bolt tilt is where the carrier bottom side at the rear of it is slammed downward as it cycles, as the carrier tilts downward the first thing the carrier impacts is the bottom of the receiver extension and this causes gouging the receiver extension near the buffer retainer. These gouges can get so bad that the rifle will have some very unusual hard to diagnose stoppages which include short stroking, failures to feed etc. I have a friend who has over 20K rounds through his piston gun and it looked like someone took a rat tail file to his receiver extension. He's also now running an experimental anti-tilt buffer as am I. I'm using this experimental buffer which addresses these tilt problems, and it is working very well at stopping bolt tilt 100% so far. The Primary Weapons conversion does have least amount of tilt for conversion units, mine wasn't bad even before using the anti-tilt buffer but the carrier did remove a little of the finish from the inside of the bottom of the receiver extension. After getting the new anti-tilt buffer I started fresh with a brand new LMT receiver extension to track any changes .
Standard direct impingement ARs don't have bolt tilt issues because the gas chamber is in the center of the carrier and when the gas is expanded in that chamber this expansion forces the bolt carrier rearward and the bolt forward until the carrier moves far enough rearward that the bolt unlocks and follower the carrier rearward.
Piston ARs have bolt tilt because they have a solid mass (not gas) impact the top front of the carrier, or they have carrier key which is impacted by the op rod which is mounted high on top the bolt carrier. The natural first movement of the carrier is to cam down slightly before starting rearward. If not addressed this is why there is gouging at the receiver extension near the buffer retainer. Some companies address this with pads at the tail end of the carrier to limit the amount of tilt.
I run my piston AR almost as wet as my standard direct impingement ARs. If you are using a sound suppressor your bolt will run cooler, but it'll still be pretty dirty along with the chamber and barrel. So “easier to clean” is a very poor excuse for wanting a piston AR. The rail, inner sides of the rail covers and portion of the barrel around the gas block on my piston AR looks as if someone airbrushed carbon all over it. So it still gets dirty, it's just in a different spot vs. a direct impingement AR. I believe if one is too lazy to clean and properly lube an AR then one should just shoot an 7.62x39mm AK. This isn't a dig at AK owners because I am one. I currently have 3 and like them a lot. AKs can be shot for a long time with very little cleaning and very little lubrication. Many of the people who think a piston AR is as reliable as an AK also believe that 5.56mm is a poor caliber for defensive use. As a whole, piston ARs aren't anywhere near as reliable as an AK as many people believe. Some are very reliable, the HK416 is one example. Piston ARs vary quite a bit from one brand to another and they aren't created equal. There is no standard for piston ARs.
Link to AR workbook:
Enjoy.
Now I'm an AR15 owner, now what?
by: Rob_S at m4carbine.net
Well welcome to the world of the evil black rifle!
Hello my name is Robb I'm also known as 'gotm4' on many gun forums.. I’ve been into ARs since the early age of 5 in 1975 after shooting a M16 with my dad (an active duty US Marine at the time, now retired).
Anyway since that day I’ve been a gun nut meaning I tried to learn everything about guns. While living at Quantico I assembled my first AR in 1987 with the help of my dad's armorer. At the time my dad worked at Firepower Division at Quantico MCCDC. Firepower Division along with Weapons Training Battalion is where the M16A2 and XM4 really came into existence. I remember seeing prototypes of both there. I visited my dad at work usually a few days a week. I got to hang out in the armory and see how the rifles and carbines were repaired, cleaned and got to shoot a lot of these guns. That is where I met LtCol Dave Lutz USMCR (now a Knights Armament employee) and Maj Jack Muth III (now a retired Colt Defense employee) my dad worked under both from 1986-1991. This is also where I met SSGT Andy Guthrie (deceased) and SSGT Owens. Owens helped me assemble my first AR. For my first ‘build’ I used a cast Essential Arms lower receiver and several parts from Quality Parts (which later became Bushmaster). I assembled a 20” HBAR using a 1x9 twist blackened stainless steel barrel. It was a very accurate rifle and I had a lot of fun with it.
Well enough about me.
With the mad rush to buy so-called 'assault weapons' due to the incoming president-elect, who has said he wants to bring back the 1994 Assault Weapons Ban and make it permanent. Because of this fear anything AR related is very hard to get right now. Some people think that on Jan 21st 2009 Obama will ban ARs, AKs etc. People are panic buying mags and ammo. Sales are up about 60% in the gun store where I work.
Lets talk a little about what you may have bought, what you didn’t buy or what you might want to buy. You may have bought a complete gun or you may have bought a complete upper and lower slapped them together, or you may have built up your AR from parts. All AR parts are not created equal.
You might be familiar with ‘The Chart’ put together by Rob Sloyer aka 'rob_s'. I wrote this article to help understand the data contained within ‘The Chart’ and to help a new AR owner figure out what to do to get the most out of their new AR15. The chart is a great resource of what to look for in an AR but those people unfamiliar with ARs might not understand it's content, and to them it might just look kind of like The Periodic Table of Elements. The Chart can be confusing to people who don't understand the things that are listed. I've written this article to help inform the new AR owner as to why he/she might want some of a particular AR features in it's columns, or why something is ‘mil-spec’.
My new AR doesn't have many Xs in The Chart, is it not 'mil-spec'?
Are 'mil-spec' features always desirable? It depends. Some things are not 'mil-spec' and would serve you just fine. For 14.5” to 16” barrels I prefer midlength gas systems. This is because they shoot softer and have less parts wear. However 'mil-spec' for and 14.5” M4 barrels is carbine length gas systems. I like LMT enhanced1 bolts for SBRs because they last longer than standard bolts. However the 'mil-spec' for bolts is the standard MPI and HP tested bolts as used in the M16-A1/A2/A3/A4, the M4 and the Mk18. 'Mil-spec' doesn't always mean the best available, it's just means that the military wants a known quality for it's equipment, in other words a baseline.
Another example: 'mil-spec' barrels for M-16s and M4s are chrome-lined and typically made from 4150 steel, do you need this? Maybe or maybe not. If you’re a Hi-power service rifle shooter or a varmint hunter and you’re really more worried about absolute accuracy. You're not worried about how long in tens of thousands of rounds this barrel will last you while maintaining 4MOA, many Hi-power service rifle shooters change barrels every 1-2K rounds and the vast majority are stainless or chrome moly steel. If you're wanting a plinker, a defensive rifle or a training carbine for classes you'll likely want a chrome lined barrel. Can chrome lined barrels be as accurate as stainless barrels? Sure they can, FN has proved this with their fantastic SPR bolt action rifles which typically shoot under 1 MOA. However the vast majority of chrome lined barrels aren’t made in the same way as FN does their bolt action rifle barrels. Typically if a shooter wants the best accuracy out of a barrel he/she will buy a stainless or chrome moly (non chrome-lined) barrel. Most chrome-lined AR barrels shoot between 1-4MOA depending on how the guns is setup. This is perfectly fine for carbines as most people are either using irons sights, Aimpoints or EOTechs. Aimpoints are typically 2-4MOA and probably 99% of AR shooters can't shoot 2MOA with an Aimpoint at 100yds anyway. I can shoot with iron sights better than I can with red dot sights, but red dot sights make me much faster which is why I use them.
Why is chrome lining used in military barrels?
Chrome lined barrels last longer than almost all other known barrels, typically last twice as long as stainless non-chrome lined barrels. Chrome lined barrels are easier to clean than most other barrels. Chrome lined barrels are much more resistant to corrosion from shooting corrosive ammo and or rusting etc.
As a whole, quite often a chrome lined barrel is less accurate than a comparable stainless or non-chrome lined chrome moly barrel. Sure some chrome lined barrels are very accurate. I have a friend that has a 20” chrome lined 1x7 twist barrel which shoots 50gr JHP American Eagle factory loads into a ½” at 100yds. It proves that chrome lined barrels can be accurate and that 1x7 twist doesn’t somehow ‘over stabilize’ light weight bullets as many people believe.
About the caliber:
Do you have or want an AR chambered in 5.56mm NATO or .223 Remington?
Do you have or want something more rare like a 5.45x39mm, 6.8SPC or 6.5Grendel?
Or do you have something which is neither something like a .223 Wylde or 5.56 Noveske Match Mod 0 chamber?
Mostly I'll be talking about .223/5.56mm NATO. The other calibers are newer to the AR and the vast majority of people aren't shooting those in the same quantities as they are .223/5.56mm
When speaking about calibers people use .223 and 5.56mm interchangeably. Just like some use 'clip' and 'magazine' and they are also not the same. Sometimes things are even more confusing with ARs. On some of their ARs Colt marks their lower receivers as .223 but then 5.56mm NATO on their barrels. Colts are chambered in 5.56mm NATO. This is okay since you can shoot .223 Remington in a 5.56mm NATO chambered barrel with no problems.
Max chamber pressure for 5.56mm NATO spec is 62,366 psi.
Max chamber pressure for .223 Remington SAAMI spec is 55,000 psi
5.56mm NATO, .223 Wylde and Noveske chambers can handle the high pressure levels of 5.56mm NATO ammo just fine. The 5.56 Noveske Match Mod 0 chamber is similar to the .223 Wylde chamber but is better suited for full auto use versus the .223 Wylde.
SAAMI spec .223 Remington chambers can be dangerous if 5.56mm NATO ammo is used in them, especially in older guns. Typically, in ARs it isn't dangerous, but .223 Remington chambers usually won't don't run well at all with 5.56mm NATO pressure ammo. The rifles will typically have failures to extract, blown primers, which will sometimes lock up the gun or make it not be able to fire. Sometimes that primer that's been blown out of the casing ends up under the trigger in the lower receiver and can keep the trigger from camming down when the shooter pulls the trigger to fire the rifle and the rifle won't fire, I've seen worse where it gets stuck up between the bolt and barrel extension which was quite hard to get it cleared and safe to fire again.
Why would someone want a .223 Remington chamber?
Because a .223 Rem SAAMI chamber is very accurate with the lower pressure SAAMI pressure .223 Remington ammo. The only guns that my wife and I have that don't have 5.56mm NATO chambers is her Noveske gun (556 Noveske Match Mod 0 chamber polygonal 1x7 twist) and our 3gun rifles. Our 3gun rifles have stainless 18” SPR profile White Oak 1x7 twist w/M4 ramps and. 223 Wylde chamber barrels.
Generally speaking for the most reliable defensive use AR, the barrel should be chambered in 5.56mm NATO, Noveske or .223 Wylde. .223 Remington has shorter lead. (The lead is the distance the projectile of a chambered round must travel upon ignition before it enters the bore of a barrel. It is measured in thousandths of an inch and is a datum of considerable interest to benchrest shooters). If 5.56mm NATO pressure ammo is fired in the .223 Remington chamber it can cause damage or failures in the rifle. The short lead drives the chamber pressure very high. Some AR barrel manufacturers have very tight .223 Remington type chambers. This is fine if all you'll ever shoot through those guns is .223 Remington SAAMI spec ammo. If you have a barrel that isn't a Noveske barrel and isn't chrome lined with 1x7 twist and doesn't have M4 feed ramps, be very suspicious if someone is telling you it's a 5.56mm NATO chamber. 5.56mm NATO, .223 Wylde and Noveske chambered guns can run with .223 Remington ammo and won't have any problems. It's like using 93 octane in a car that only requires 87 octane, it doesn't really hurt anything but do it the other way around and it could cause problems.
Things to consider if you're reading this and haven't yet bought your AR:
What is your ARs purpose?
Is it for use at training courses?
Is this AR for competition? 3gun or Hi-power? (They differ greatly)
Does your rifle have a dual purpose role?
Do you just want an AR as something to show off during the holidays or because you think ARs will be banned?
What length barrel do you want?
Do you want a carbine (less than 18” barrel?)
Do you want a full size or bigger rifle?
What length gas system do you want? (pistol, carbine, midlength, intermediate, rifle)
How many rounds per month/week/year will you shoot?
How much do you want to spend?
Most AR owners shoot no more than about 1K rounds per year with the vast majority shooting one eighth to one half of that. If that's all you'll shoot, you probably don't need to worry much about anything other than buying decent ammo and magazines and a 1 oz bottle of oil.
For the last 4yrs shooting competitively, training and recreational shooting I average 12-20K rounds per year depending on how many multi-gun/3gun matches and training courses I attend per year. My goal for training is to take at least one carbine/pistol class per year. My wife averages 1-2K rounds per year. My wife and I own 7 functional ARs and have two other lowers that aren't built into rifles. So you can see even with the large amount of shooting that I do, the amount of rounds is spread out among the different rifles. The rifles/carbines I shoot the most currently are my 3gun rifle, 10" SBR, Colt w/PWS piston conversion, in that order. Even with as much shooting as I do, I don't get wrapped around the axle about the barrel steel etc. as some folks do. Sure some are better than others, my 12.5” SBR it's a 1x9 twist cut down from a 14.5” Bushmaster barrel. I 'shaved' the front sight base down so it fits under the Daniel Defense RIS II Mk18 rail. With 55gr ammo, this barrel with my suppressor is more accurate than my LMT 10” SBR. Is my Bushy 12.5” barrel as high quality as a Colt barrel? No, but for me it gets the job done. Depending on what you are doing with an AR, you really have to know your priorities.
If your AR is used for training/personal defense or is a jack of all trades rifle and you'll shoot more than 1K rounds per year I would highly suggest a chrome lined barrel. I would also suggest the following:
Use a MPI and HP tested bolt (if replacing yours I'd suggest a BCM or LMT bolt).
Ensure the carrier key is torqued and staked sufficiently.
If your carbine has a collapsible stock I would suggest having the castle nut end plate staked into the castle nut.
Make sure your ejector and extractor are of high quality and have the correct extractor spring and black extractor spring buffer installed with it. If you're using a Colt, LMT or BCM bolt you'll already have top quality parts. In ARs with carbine length gas systems you should run a black extractor spring buffer and a 5-coil extractor spring. If you have an AR with a midlength or rifle length gas system, it will work with a blue or black extractor spring buffer and the smaller extractor springs. I use the 5-coil ones in all my ARs that have standard type (non-LMT enhanced) bolts regardless of barrel/gas system length.
All of these things are done on 'tier 1' ARs. Tier 1 basically meaning a Colt or FN. Both are truly Tier 1 'mil-spec' guns because the US Military uses both. FNs aren't available to the public so we really have to rule them out. The next closest brand is LMT.
Will another brand of AR other than a Colt or LMT serve you well?
Sure. Especially if you fall into that 1K rounds or less per year category.
Example, lets say all you can find is brand X, Y or Z, and you just got it because that's all you could find and you want this as reliable as possible because you'll use this gun for training classes or self defense. Lets say the rifle doesn't have as many Xs as does a Colt or LMT rifle in The Chart.
Things I would do or check on non-Colt or non-LMT brands:
If the carbine you bought doesn't have a HP and MPI tested bolt I'd buy a BCM or LMT bolt, firing pin, cam pin and use them and keep the factory bolt, firing pin and cam pin as spares. If you ever take a carbine class, you should have these parts as spares anyway. If you bought a rifle length AR, the bolt is a little less of a concern. 20” guns have the best reliability of all ARs. Bolt life is the longest on the 20” or longer rifles. You should still make sure that you have a good cam pin, firing pin, extractor and ejector and springs for each. An easy way to make sure you're getting good parts like this is from BCM, they offer a SOPMOD bolt upgrade kit which includes a proper 5 coil extractor spring, black ex. spring buffer, a Crane O-ring, a extractor pin and a set of gas rings. Don't use Crane o-rings on anything with a gas system longer than carbine length, it can cause feeding problems on slower running guns. Then take the AR out and shoot it, if it'll run for more than 500 rounds without any stoppages then you're good to go.
Your spares kit should have the above plus a spare buffer spring, a hammer, trigger and disconnector and their springs. A spare bolt catch kit, mag catch kit, at least two take down pin detents and springs as well a selector detent and spring.
On the other brands of unknown quality (few Xs on The Chart) I'd either replace the carrier key with a BCM, LMT or Colt carrier key along with new carrier key screws or at a very minimum remove the factory carrier key, degrease it, lap the bottom of it, this means using a whetstone to remove the finish on the bottom of the key to ensure it's absolutely flat and not warped and will now seal well against the bolt carrier. Apply red loc-tite or better yet Rocksett to the bottom of the carrier key, reassemble and torque the carrier key screws to 50-55in lbs (higher than the USMC technical manual I know). Stake either with a chisel and hammer or best with a Ned Christiansen MOACKS tool. Staking is pushing some of the carrier key metal into the screw heads to keep the screws from loosening due to heat and vibration. If you test fire the gun a few hundred rounds of high quality preferably NATO pressure ammo and even with the above improvements it still doesn't run well, I'd ream the chamber with Ned Christiansen 5.56mm NATO neck and throat reamer. If the rifle has a lot of Xs in the chart in all likelihood you have the correct size gas port for 5.56mm NATO pressure ammo. If it has fewer Xs in the columns of The Chart, more than likely you should replace a CAR buffer with a H or H2 buffer if you're going to be shooting 5.56mm NATO pressure ammo. The lower end ARs use larger gas ports for people who buy weaker .223 Rem pressure ammo.
CAR buffers are 3oz
H buffers are 3.8oz
H2 buffers are 4.6oz
H3 buffers are 5.6oz
Now that you're a new AR owner, are you also going to jump into NFA?
Meaning do you want to register your AR as a short barreled rifle (SBR), buy a sound suppressor or buy a registered full auto lower?
If so you will definitely want to ensure that your AR is up to the task. As above, you should be using a MPI and HP tested bolt with top quality ejector and extractors. Depending on your barrel length and brand of barrel, you should use a H to H3 buffer with your AR if running a sound suppressor.
SBRs are harder on everything vs. a 16" carbine. 16" guns cycle faster than 20" guns, and SBRs cycle faster still. Why is this? This is because the original AR was a 20" rifle length gas. Carbine length gas ARs are running almost double the gas pressure of a 20" rifle gas gun. This shorter gas system adds much more pressure and heat to the bolt and the bolt velocity is faster the shorter you go with the barrel. Bolt life is shorter and other components wear out faster in the shorter guns. It's almost unheard of to hear of a 20" AR using a MPI and HP bolt to break a bolt. Carbine length ARs will break bolts from 3K to 20K rounds depending on you're firing schedule. It gets worst the shorter you go under 16". 10" guns wear things at a rapid pace and even worse if you use a sound suppressor.
Sound suppressors add even more gas pressure to the already fast cycling high pressure short gas system. Example, if running suppressed my 10" will wear out a set of gas rings in about 1K rounds. If I shoot it unsuppressed I can easily get 2K rounds out of the rings. Cam pins if running suppressed look beat to hell in about 1.5K rounds, if unsuppressed 3K rounds. Because of this added wear, I use a LMT enhanced bolt which has relieved bolt lugs and and upgraded extractor which has dual extractor springs. This gun has only ever had a stoppage twice (I don't like the word 'jam'. Jam is what you put on biscuits). Both stoppages were due to shooting Radway Green ammo when I didn't have the suppressor mounted. Both stoppages were failures to eject because the gun short cycled. Short cycles are where the bolt carrier doesn't move far enough rearward in its travel to eject and/or pick up the next round in the magazine to feed. Radway Green ammo has a pressure spike that drops very quickly (Radway Green is made for the British SA80A2) and won't work in most of my ARs unless I'm running them with the sound suppressor. This ammo does work in my piston Colt/PWS AR as well as my Arsenal SLR-106FR (5.56mm AK).
If your AR is for competition, varmint hunting you can really set it up any which way you want.
If your AR is just for showing off, or you just bought it because you think they might be banned and you aren't actually going to shoot it then don't change a thing. Do what you want since it isn't a life saving tool.
Piston ARs:
If you are planning to build or buy a SBR or full auto or use a sound suppressor, I would suggest considering a piston gun.
Many people think they need a piston AR or they need to convert their standard AR to piston. Many of these people use the excuse that piston ARs run better than direct impingement ARs or run cleaner. This is not the case. Piston guns have their own sets of known problems. These are just different problems and weakness areas vs. standard direct impingement ARs.
Piston guns get dirty as well just not at the bolt, bolt carrier and in the upper receiver, piston ARs are more forgiving of the lack of lubrication (because the bolt and carrier aren't getting as hot and hot gas isn't blown into the action), they can be run with a little less lubrication than direct impingement ARs. I have the Primary Weapons carbine length piston conversion on my Colt 6920 upper. It gets plenty dirty. After a thousand rounds or so it looks like I've airbrushed carbon all over the gas block and the rail and barrel near the gas block. This is where it bleeds off the excess gas not used to cycle the bolt. If shooting without a glove on my left hand it gets very hot in this area pretty quickly, actually hotter than comparable direct impingement ARs.
Many piston ARs suffer from bolt tilt. Bolt tilt is where the carrier bottom side at the rear of it is slammed downward as it cycles, as the carrier tilts downward the first thing the carrier impacts is the bottom of the receiver extension and this causes gouging the receiver extension near the buffer retainer. These gouges can get so bad that the rifle will have some very unusual hard to diagnose stoppages which include short stroking, failures to feed etc. I have a friend who has over 20K rounds through his piston gun and it looked like someone took a rat tail file to his receiver extension. He's also now running an experimental anti-tilt buffer as am I. I'm using this experimental buffer which addresses these tilt problems, and it is working very well at stopping bolt tilt 100% so far. The Primary Weapons conversion does have least amount of tilt for conversion units, mine wasn't bad even before using the anti-tilt buffer but the carrier did remove a little of the finish from the inside of the bottom of the receiver extension. After getting the new anti-tilt buffer I started fresh with a brand new LMT receiver extension to track any changes .
Standard direct impingement ARs don't have bolt tilt issues because the gas chamber is in the center of the carrier and when the gas is expanded in that chamber this expansion forces the bolt carrier rearward and the bolt forward until the carrier moves far enough rearward that the bolt unlocks and follower the carrier rearward.
Piston ARs have bolt tilt because they have a solid mass (not gas) impact the top front of the carrier, or they have carrier key which is impacted by the op rod which is mounted high on top the bolt carrier. The natural first movement of the carrier is to cam down slightly before starting rearward. If not addressed this is why there is gouging at the receiver extension near the buffer retainer. Some companies address this with pads at the tail end of the carrier to limit the amount of tilt.
I run my piston AR almost as wet as my standard direct impingement ARs. If you are using a sound suppressor your bolt will run cooler, but it'll still be pretty dirty along with the chamber and barrel. So “easier to clean” is a very poor excuse for wanting a piston AR. The rail, inner sides of the rail covers and portion of the barrel around the gas block on my piston AR looks as if someone airbrushed carbon all over it. So it still gets dirty, it's just in a different spot vs. a direct impingement AR. I believe if one is too lazy to clean and properly lube an AR then one should just shoot an 7.62x39mm AK. This isn't a dig at AK owners because I am one. I currently have 3 and like them a lot. AKs can be shot for a long time with very little cleaning and very little lubrication. Many of the people who think a piston AR is as reliable as an AK also believe that 5.56mm is a poor caliber for defensive use. As a whole, piston ARs aren't anywhere near as reliable as an AK as many people believe. Some are very reliable, the HK416 is one example. Piston ARs vary quite a bit from one brand to another and they aren't created equal. There is no standard for piston ARs.
Link to AR workbook:
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