The Essentials of a Precision AR-15

[Molon]

The Essentials of a Precision AR-15


http://www.box.net/shared/static/mla3p170ls.jpg


Without making this overly complicated, you need three basic components for a semi-automatic AR-15 to produce its best mechanical accuracy (technically, precision): a match-grade barrel, a quality free-float handguard and match-grade ammunition, preferably hand-loads tuned for your barrel. (The free-float handguard doesn’t improve the accuracy of the barrel per se, it simply prevents any outside influence from detracting from the accuracy of the barrel.) Anything after that will not immensely improve the mechanical accuracy of the semi-automatic AR-15, but several things can help you, the shooter, shoot to the level of the intrinsic accuracy of your semi-automatic precision AR-15.



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While there are certainly gifted individuals among us that can do amazing things with iron sights, most of us will benefit from using a quality, high-power scope to achieve the highest level of accuracy from a precision AR-15. In order to hit the exact same spot on the target every time, you have to be able to see that you are holding on the exact same spot every time. It’s also important for the scope to be mounted at the proper height and at the correct eye-relief for the particular scope. One of the most common errors I see with scopes mounted on AR-15s is the scope not being mounted far enough forward for its eye-relief. Also, in order to maintain that exact hold throughout the trigger pull, it helps not to be fighting a heavy, gritty, stock trigger. There are a variety of aftermarket triggers now on the market for both standard size trigger pins and the larger Colt trigger pins. Personal preference will definitely play a role in trigger selection. Among the two-stage triggers, I’ve found the Geissele triggers to be the smoothest, lightest, most consistent and most reliable. For single-stage triggers, it’s hard to beat the JP Enterprise Fire Control System. Keep in mind that the JP trigger does require fitting.

Following the scope and trigger selection, some shooters will find that items like aftermarket grips and stocks will help them achieve a better “fit” with their AR-15. (Shooters don’t all come in the exact same size and shape.) Once you’ve put your precision rig together, you have to find a match-grade factory load that your barrel “likes” or better yet, develop a match-grade handload for it.

A semi-automatic AR-15 is not going to shoot as accurately as a precision bolt-gun, but today’s precision AR-15s are capable of a level of accuracy that is truly outstanding for a semi-automatic rifle. The 10-shot group pictured below was fired from one of my Krieger barreled semi-automatic AR-15s from a bench-rest at a distance of 100 yards. The barrel has a 1:7.7” twist. I used Sierra 55 grain BlitzKings that were hand-loaded on a Dillon XL-650 progressive press. The load was developed using the Accuracy Node Detection Technique. The group has an extreme spread of 0.452”.



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[CoryCop25]

Very nice post. I am more of a combat shooter but this proves the ability of the AR platform.

[KG_mauserman]

I'm curious how much the bolt can affect the accuracy of the AR-15 platfrom. I have an LMT enhanced bolt and noticed that compared to a standard bolt it has smaller lugs. It would seem that how tightly the bolt locked to the barrel would play a big part on how accurate the rifle was. If you have a match grade chamber, but a sloppy bolt could that affect accuracy?

[Ratfink]

I know this is a forum and im being the guy i cant stand by saying this but

those groups are attainable with a high end 14.5-16 in carbine i shoot those groups constantly with my duty rifle

noveske afghan 14.5 in
ssa 77gr sierra otm
US optics SN-4S 1x4
factory bolt group
SSA 2 stage trigger

imho nothing very exotic and my 7 year old daughter is shooting groups in the 1in area

im not shure how much there is to gain with a higher end bolt group

[Nevermiss]

As always, your posts are a joy to read!

Thanks for sharing.

[epete]

Molon,

Would you care to elaborate on the Accuracy Node Detection Technique?

Google only turned up articles on Lymph nodes and circuitry.

Thanks.

[Belmont31R]

I'm curious how much the bolt can affect the accuracy of the AR-15 platfrom. I have an LMT enhanced bolt and noticed that compared to a standard bolt it has smaller lugs. It would seem that how tightly the bolt locked to the barrel would play a big part on how accurate the rifle was. If you have a match grade chamber, but a sloppy bolt could that affect accuracy?



Its like not a bolt gun where the bolt face and lugs are part of the entire bolt group. The AR bolt group is basically 2 main pieces where a bolt gun is one main piece. The AR bolt basically floats in the bolt carrier, and when in the locked position can be moved slightly just be finger pressure.

I do not believe you would notice any difference between an in spec and within head space USGI carrier and the fancy BCG's due to the above reasons. With a bolt gun accuracy can be improved by blueprinting/truing the action. Its just not possible in an AR to get the tight fit a quality bolt gun has.

[KG_mauserman]

Thanks for the input. I have been thinking about it all day and what you said makes sense.

[MistWolf]

As always, great post Molon


Its like not a bolt gun where the bolt face and lugs are part of the entire bolt group. The AR bolt group is basically 2 main pieces where a bolt gun is one main piece. The AR bolt basically floats in the bolt carrier, and when in the locked position can be moved slightly just be finger pressure.

I do not believe you would notice any difference between an in spec and within head space USGI carrier and the fancy BCG's due to the above reasons. With a bolt gun accuracy can be improved by blueprinting/truing the action. Its just not possible in an AR to get the tight fit a quality bolt gun has.The laws of physics don't change just because we're talking about the AR. The interface between the bolt lugs and the recess is important regardless if it's bolt & carrier design or simply a bolt.

Being a two piece bolt design isn't why headspace is within spec when changing out barrels & bolts. It's because the tolerances are tightly controlled. I believe it's the barrel, barrel extension & barrel nut design that allows the tolerances to be held.

Not all bolt actions have a one piece bolt body. As I understand it, the Savage use a two piece bolt and a barrel nut. Mauser type bolt actions require the barrel to be screwed into place to a certain torque spec. This makes it difficult to match actions, barrels and bolts so that they are interchangeable without it changing the headspace. Further complicating things is the bolt locks into recesses cut in the action.

I don't have an AR with me to check, but I don't think you can move an AR bolt back & forth when it's locked into battery That would allow the headspace to change and could cause dangerous fluctuations in pressure. It would also allow the lugs and recesses to be battered to death with each shot. The bolt carrier, yes. That can be moved slightly without unlocking the bolt.

The only way to determine if a National Match carrier will improve accuracy is to shoot it alongside a normal carrier. The theory is sound as it reduces the axial play of the bolt carrier within the receiver

[Failure2Stop]

those groups are attainable with a high end 14.5-16 in carbine i shoot those groups constantly with my duty rifle

noveske afghan 14.5 in
ssa 77gr sierra otm
US optics SN-4S 1x4
factory bolt group
SSA 2 stage trigger

imho nothing very exotic and my 7 year old daughter is shooting groups in the 1in area

im not shure how much there is to gain with a higher end bolt group

I don't know, but it seems like you are agreeing with Molon here:
Great barrel? Check
Ammunition matched to barrel? Check
Free floated barrel? Unsure by specs, but without variable pressure it's irrelevant.

If you are saying that an "Uber-Bolt" is unnecessary, I agree.

[bgrundy]

Thanks for posting this. Good stuff.

I'd be more interested in seeing changes in grouping with a variety of ammo out at 200 or 300 yds with an AR/.223 platform. 100yds seems a bit short to get a good idea of comparative bullet behavior. Right now I'm limited to 100yds as well, but I'm anxious to see what my new Afgan 14.5 will do with Black Hills match vs. Privi SS109 stuff out at 200, when I get a chance.

I'm new to this board and completely hooked, BTW. Thanks!

[JimmyB62]

I know this is a forum and im being the guy i cant stand by saying this but

those groups are attainable with a high end 14.5-16 in carbine i shoot those groups constantly with my duty rifle

noveske afghan 14.5 in
ssa 77gr sierra otm
US optics SN-4S 1x4
factory bolt group
SSA 2 stage trigger

imho nothing very exotic and my 7 year old daughter is shooting groups in the 1in area

im not shure how much there is to gain with a higher end bolt group

I have found that 10 shot groups under an inch from any AR are not very common. 10 shot groups at under 1/2" are spectacular. I have a hard time with your statement that you do it regularly especially with the SSA load.

[Magic_Salad0892]

I have a harder time believing that he does it with a Noveske Afghan.

Noveske barrels are usually 1-1.5 MOA barrels.

I sooooo want a Kreiger barrelled bolt action gun, or AR. :)

[jmart]

Molon,

Would you care to elaborate on the Accuracy Node Detection Technique?

Google only turned up articles on Lymph nodes and circuitry.

Thanks.

Google "Ladder Testing". It's really designed for handloaders who can fine tune powder charges in small increments.

The principle is that during firing, the barrel will whip as the bullet travels the length of the barrel. If the barrel is between the upper and lower nodes, it's whipping quicker compared to when it's whipping as it decelerates to a full stop up or down and changes direction. The idea is to find a powder charge that results in bullet exiting at the muzzle during one of these slow, decelerating whip nodes , ideally when the barrel is at full stop during a direction change. Dispersion will be minimized during these nodes compared to when the barrel is in mid-whip.

The technique involves loading a round or two with a particular charge, and subsequent rounds at approx .2g increasing charges. Shoot the rounds in order and using a spotting scope/high mag optic, plot on a clean target target where each round hits. What you should find is that charges that equate to mid-whip cycle will plot in a linear fashion, whereas rounds that equate to and end-of-whip/node cycle will cluster tightly. This then becomes your accuracy load, and you should also find that your load is a bit fogiving -- you can be off a tenth or two in powder weight, yet the load will still be accurate.

[johnson]

Molon,

Would you care to elaborate on the Accuracy Node Detection Technique?

Google only turned up articles on Lymph nodes and circuitry.

Thanks.

There's a thread talking about it in the SH reloading section.

http://www.google.com/search?hl=en&q=Creighton+Audette+ladder+test&btnG=Search&aq=f&aqi=&aql=&oq=&gs_rfai=

http://www.the-long-family.com/OBT_paper.htm

[hikeeba]

Good stuff, Molon. Thanks for taking the time to put that together. Impressive 10-shot group, as well. May I ask what scope power you used to achieve that group? May I ask what sort of chamber that barrel has?


And for Molon and everyone else to consider/ponder/comment on/yell at me about-

I have seen the three Bs of accuracy mentioned (arranged in order of their importance): Barrel, bullet, and brass. How much does the brass matter, and why? And are we talking about differences between brands of new brass, or brands in general regardless of new, once-fired, or whatever?

When I've seen the three Bs thrown out in conversation, it has been mostly cut and dried/black and white. Barrel - you need to have a high-quality, match-grade barrel. Bullet - for best accuracy you need to find a bullet your barrel likes to send. Brass - ??? I've never seen any elaboration on the brass aspect other than 'used good brass.' Are they referring to the contents of the brass; as in the primer and the powder?

And I haven't seen the free-floated handguard wrapped into the barrel point. I might be wrong, but I think the free-floated handguard has more to do with realizing mechanical accuracy potential than brass by itself.



I noticed Molon pictured two different rifles. One has a muzzle device, the other does not. Does a muzzle device (hider, comp, hider/comp) detract from mechanical accuracy potential at all? If so, are there devices that are worse that others in this context; models that may hamper mechanical accuracy potential more than others? I know swapping different muzzle devices onto a given barrel may change POI, and that a good target crown is probably the best thing if one wants to achieve true precision. But most of the higher-end (by higher-end, I'm thinking reasonable higher-end like Noveske, Ranier, LW/LaRue, WOA, BCM) barrels on the market are threaded for a muzzle device. And some of those barrels are touted as being MOA or better. Are muzzle devices insignificant in the accuracy chain, and I'm just thinking about them too much?



And what about the chamber and how it relates to accuracy? And what the heck are the specs of the 5.56 NATO Match Chambers (USMC SAM-R Chamber)?

[MistWolf]

Actually, right out of the gate Molon posted Without making this overly complicated, you need three basic components for a semi-automatic AR-15 to produce its best mechanical accuracy (technically, precision): a match-grade barrel, a quality free-float handguard and match-grade ammunition

[epete]

Google "Ladder Testing". It's really designed for handloaders who can fine tune powder charges in small increments.

Thanks for your explanation. I had a feeling that this was what we were discussing. You can't argue that accuracy node detection technique doesn't sound more impressive than ladder testing.:)


There's a thread talking about it in the SH reloading section.

http://www.google.com/search?hl=en&q=Creighton+Audette+ladder+test&btnG=Search&aq=f&aqi=&aql=&oq=&gs_rfai=

http://www.the-long-family.com/OBT_paper.htm

Thanks, saved for later.

[Molon]

Molon,

Would you care to elaborate on the Accuracy Node Detection Technique?

Google only turned up articles on Lymph nodes and circuitry.

Thanks.

The Accuracy Node Detection Technique is simply a tool to aid hand-loaders in determining the specific powder charge that is most likely to deliver the highest level of accuracy (technically precision) from their barrel with a particular powder. Those of you familiar with Creighton Audette’s Incremental Load Development Method (Ladder Test) or Dan Newberry’s Optimal Charge Weight method may recognize that the Accuracy Node Detection Technique is based on the same underlying concepts that those methods are.

The Accuracy Node Detection Technique (ANDT) is basically a refined, statistically significant version of the ladder test/optimal charge weight method and the ANDT is not dependent upon “interpreting the data” like the previous methods. The ANDT uses much larger effective sample sizes for a greater confidence level and utilizes the mean radius to measure the dispersion of composite shot groups to obtain a more precise identification of the accuracy node of a given barrel/powder combination.

[Molon]

To the Moderator who moved this thread from the “AR General Discussion: General topics relating to the AR” forum, to the “Precision Rifle: Bolt guns” forum,

A semi-automatic AR-15 is not a bolt gun.

Molon

[hikeeba]

Dang. Almost had to call for the dogs to help me find this thread again... :confused:


Actually, right out of the gate Molon posted Without making this overly complicated, you need three basic components for a semi-automatic AR-15 to produce its best mechanical accuracy (technically, precision): a match-grade barrel, a quality free-float handguard and match-grade ammunition

MistWolf, I wasn't referring to Molon when I addressed sources taking about the Three Bs of Accuracy. I was merely pointing out that it has been my experience that some other folks haven't mentioned the free-float handguard as a major component in realizing mechanical accuracy potential of an AR-15. I thought Molon's post was spot-on.


Thanks again, Molon, for starting this thread. I recently took a step towards the 'better accuracy' realm, and this thread is both timely and very relevant to my interests.

[MistWolf]

...MistWolf, I wasn't referring to Molon when I addressed sources taking about the Three Bs of Accuracy. I was merely pointing out that it has been my experience that some other folks haven't mentioned the free-float handguard as a major component in realizing mechanical accuracy potential of an AR-15. I thought Molon's post was spot-on...Gotcha.

Molon, your post came at a good time for myself as well. I'm gathering the parts to build an accurate rifle length AR

[Molon]

Dang. Almost had to call for the dogs to help me find this thread again... :confused:




Exactly my point about moving this thread from the AR General Discussion forum.

[decodeddiesel]

To the Moderator who moved this thread from the “AR General Discussion: General topics relating to the AR” forum, to the “Precision Rifle: Bolt guns” forum,

A semi-automatic AR-15 is not a bolt gun.

Molon

Agreed. This discussion is especially pertinent to AR General Discussion IMO.

[constructor]

Good trigger and a real long range cartridge doesn't hurt.
6mmBR or 6BRX can have 100" less drop and 20" less drift than a 308 shooting 175 SMks at 1000yds.
6BRX mag and function test video- 95gr SMK with a BC of .480 doing 3180fps from a 22" barrel.
http://www.youtube.com/watch?v=je3ulQuG3S0

[boltcatch]

Well launching the projectile in a consistent direction, having the projectile travel the same path far down range consistently (wind drift and whatnot), and how much leeway the shooter has for ranging error (bullet drop) are 3 different issues with a bunch of different solutions.

Within a specific caliber you sometimes cannot greatly improve all three of those things at once, so yes, moving to a different caliber can improve your results downrange. I'm happy enough with my 75gr OTM's.

[11B101ABN]

Great info, thank you much.

[J Krammes]

Good thread... I built an 18" AR recently for long range purposes. I used a White Oak SPR barrel for the build. I just picked up a Vortex 6.5-20x50 Viper. I just need a mount and I can get shooting. I did do somewhat of a barrel break in, but the scope I used sucked and I have not had it out since. What type of mounts do you guys like for this type of platform? I was planning on getting an American Defense Recon unless I get a better recommendation.

Jeremy

[mizer67]

Molon,

Did you have the Krieger profiled and cut down, or is that thier standard 20" HBAR DCM version?

[Molon]

Molon,

Did you have the Krieger profiled and cut down, or is that thier standard 20" HBAR DCM version?


The AR in the top picture in the original post has a 20" Noveske HBAR. The bottom picture in the origianl post has a 24" Krieger VarMatch barrel. I also own a couple of the 20" Krieger DCM HBARs, which of course are outstanding barrels too.


20" Noveske HBAR.

http://www.box.net/shared/static/dp17jk7dd8.jpg




24" Krieger VarMatch

http://www.box.net/shared/static/psau3igm35.jpg



20" Krieger DCM HBAR

http://www.box.net/shared/static/f0ogpqkk49.jpg




16" Krieger "DCM" HBAR

http://www.box.net/shared/static/dthiv4s3pj.jpg



....

[DTHN2LGS]

Good thread... I built an 18" AR recently for long range purposes. I used a White Oak SPR barrel for the build. I just picked up a Vortex 6.5-20x50 Viper. I just need a mount and I can get shooting. I did do somewhat of a barrel break in, but the scope I used sucked and I have not had it out since. What type of mounts do you guys like for this type of platform? I was planning on getting an American Defense Recon unless I get a better recommendation.

Jeremy

The only suggestion I can make is a LaRue mount. They are the shit.

[sadmin]

Digging up an old post to initiate a discussion to see if anything has changed / developed in the last decade in this context. Have certain accessories / attachments been introduced that are now "highly recommended"?

If you read this - what does your rifle setup look like now compared to 2010 or previous? Barrel, optic magnification / brand, etc.. - realizing this is user specific, just attempting to incite from fresh discussion.

I can report that in the last 12 years, I no longer have an 18" rifle for 400+ yards. I no longer have an optic over 1-10x on an AR platform.

Inb4 the OGs just reply with "NO" ;)

[chuckman]

More companies making comparable barrels, more good choices on optics, maybe a couple more choices with quality triggers.

[markm]

This is Pappabear's Geissele, and about the sweetest precision AR set up I've shot.

The main features are the Glass (obviously), the trigger, a good shooting barrel, Atlas pod, and a good suppressor.

https://i.imgur.com/tuQRyFr.jpg

[sadmin]

Mark - what are you stretching that out to? +700y?
At what range do you opt for a heavier caliber?
Being in E.TX.. Ive pretty much abandoned any AR I had that was over 16" with higher end magnification that I had setup for 500y+ due to limited line of sight / bullet impedance by way of foliage.

[markm]

We shoot it out to 1000 yards. Anything with glass greater than an ACOG we will at least try to get 1000 yard hits. It makes coming back into 500-700 yards less challenging. We're not shooting amazing groups at 1000 due to less than perfect wind conditions where we shoot. But we do aim to hit an IPSC size steel.