Featured How to build an AR-15 - thearmsguide.com

Published on July 6th, 2013 | by Nate Schultz (nsz85)

104

How to Build an AR-15: Beginner’s Guide

You do not always have to go to a gun store to purchase an AR-15. Surprised? I know I was when I first ventured into the hobby of building custom AR-15s. Some of you may not know, but building your own AR-15 is actually quite simple. However, if you do not know anything about the process, or where to start, you have come to the right place. I am going to start this “How to Build an AR-15” series off with a list of frequently asked questions that I receive from individuals starting out with the hobby and possibly wanting to build their first AR-15.

Building an AR-15 FAQ

Q: Are there any rules or laws for building my own AR-15?
A: Only the same ones that apply to purchasing a factory assembled AR-15 in your state.

Q: Do I need to register my AR-15?
A: There is currently no Federal firearms registry, but you’ll need to verify the registry laws by state (e.g., New York does require registry of “assault rifles,” including standard AR-15 rifles).

My AR-15 - thearmsguide.com

Me smiling after taking some of the first shots with the first AR-15 that I built for myself. Photo of me courtesy of paul-vincent.com

Q: Do I need to be licensed or be a gunsmith to build my own AR-15?
A: Not unless you’re milling the lower receiver yourself.

Q: How many AR-15s can I build?
A: As many as you would like to—whichever comes first.

Q: If I build an AR-15 for myself, can I then sell it?
A: The same laws for private sales of firearms apply to selling AR-15 rifles. Check your state laws.

Q: How do I buy a “stripped” or “blank” AR-15 lower receiver?
A: You will need to find a dealer that sells AR-15 lower receivers. Said dealer can be local to you, or online.

Q: Can I buy all the parts online and have them shipped to my home?
A: This is a long one, so get comfortable. Yes and no. All of the components for your AR-15 build can be shipped directly to you at your home except the lower receiver.

The AR-15 lower receiver is the only component that is considered the “gun”. Therefore, when purchasing a lower receiver for your AR-15 build, you will have to go through the same channels as when purchasing a firearm in your state.

For example, in my state of Minnesota, if I order a stripped AR-15 lower receiver online, I will have to provide the seller with a copy of an FFL (Federal Firearms License) and the address to aforementioned FFL. In other words, I just have to call my local gun shop and ask them to fax a copy of their FFL to the seller. The seller will then collect money from me for the receiver, and then ship it to my local gun shop. When the gun shop calls me to tell me that my lower receiver has arrived, I will go there and fill out the ATF form to make sure I can legally own a firearm, pay a transfer fee (this fee is usually less than $30), and take my new AR-15 lower receiver home (thankfully, Minnesota has no waiting period for long gun purchases).

If I decide not to order online, and I know of a gun shop that stocks lower receivers nearby, I can just go purchase it directly from that store, and then fill out the necessary ATF form, just as I would for purchasing any other kind of firearm.

Q: What parts make up an AR-15 that I would have to purchase to build one?
A: There are a variety of different types of AR-15 builds, so this list will not work for all builds. However, I put together a list of components for building a typical M-4 style AR-15 with a stripped lower receiver, and stripped upper receiver:

  1. AR-15 lower receiver.
  2. AR-15 upper receiver.
  3. Lower receiver parts kit.
  4. Upper receiver parts kit.
  5. Lower receiver extension (aka: the buffer tube).
  6. Buffer.
  7. Buffer spring.
  8. Barrel & gas block/gas system (a carbine length gas system would be typical for this build).
  9. Handguards (length will depend on what length gas system you chose on your barrel: carbine, mid-length, or rifle).
  10. Bolt carrier group (carrier, bolt, firing pin, cam, extractor, ejector and spring).
  11. Collapsible (or fixed, if you prefer) buttstock.
  12. At least one magazine (be sure to check your state laws for magazine capacity limits).

Q: What is the difference between a forged lower receiver and a billet lower receiver?
A: With a forged lower receiver, the metal is “smashed” into the desired form while it is red hot. This compresses the metal and makes it very strong.

Billet lower receivers are machined from a single block of metal and tend to have a more custom, aesthetically pleasing appearance to some. It also tends to have the trigger guard built in, meaning it is not removable. They also tend to cost considerably more than a forged lower. Billet lowers may not have quite the tolerance that forged lowers, but by no means are they to be considered “weak.”

MEGA Billet Lower - thearmsguide.com

This is an example of a billet AR-15 lower receiver. Image courtesy of megaarms.com

MEGA Forged Lower - thearmsguide.com

This is an example of a forged AR-15 lower receiver. Image courtesy of megaarms.com

 

Q: How do I know which lower receiver to purchase? What “brands” are good?
A: There are a tremendous amount of different lowers out on the market, but not every lower is made by the company that has its name on the side. You would be surprised at how many lowers from different companies actually come from probably less than a dozen machine shops.

At present, this is the list of which manufacturers produce lowers for which companies:

Lewis Machine & Tool

  • LMT
  • Lauer
  • DS Arms
  • PWA
  • Eagle
  • Armalite
  • Knights Armament
  • Barrett

Continental Machine Tool

  • Stag
  • Rock River Arms
  • High Standard
  • Noveske
  • Century (New)
  • Global Tactical
  • CLE
  • S&W
  • MGI
  • Wilson Tactical
  • Grenadier Precision
  • Colt

LAR Manufacturing

  • LAR
  • Bushmaster
  • Ameetec
  • DPMS
  • CMMG
  • Double Star
  • Fulton Armory
  • Spike’s Tactical

JVP

  • Double Star
  • LRB
  • Charles Daly

Mega Machine Shop

  • Mega
  • GSE
  • Dalphon
  • POF
  • Alexander Arms

Olympic

  • Olympic
  • SGW
  • Tromix
  • Palmetto
  • Dalphon
  • Frankford
  • Century (Old)

Sun Devil

  • Sun Devil forged billet receivers

Superior

  • Superior Arms
  • Lauer (New)

Aero Precision

  • Aero Precision

Considering that almost all AR-15 lower receivers are made to a very specific tolerance, based on military specifications (mil-spec), my advice is to choose whichever AR-15 lower receiver that has a roll-mark (or logo) that you think is “coolest” or is most appealing to you personally.

Q: Some barrels say they are chambered in 5.56 and some say they are chambered in .223. What is the difference?
A: Basically, the rule of thumb is this: a rifle chambered for 5.56 can shoot both 5.56 and .223 ammunition. A rifle chambered for .223 can only shoot .223 and not 5.56. For the full story on 5.56 vs. .223, check out this article by Destinee.

Q: What does barrel twist mean? 1:7 and 1:9? Ratio? What?
A: Confused? Yeah, this one is kind of technical but I will keep it simple. When choosing a barrel twist ratio, you will want to choose one that best matches the type of ammo you would normally be shooting. What the ratio means, such as 1:7 for example, is that when the bullet travels down the barrel, it will make one complete spin (via the rifling) every seven inches.

AR-15 1:7 vs 1:9 Ratio - thearmsguide.com

(Fig. 1a)This is great information about shooting 1:7 vs. 1:9 twist ratios at long distances through your AR-15.

This is one of the most hotly debated topics about AR-15 rifles. Personally, I chose to go with 1:7 because it gives me the option of shooting the heavier rounds. Because 55gr .223/5.56 is the most common bullet weight available (that’s the weight used in XM193 military ball 5.56×45 ammo), and the most frequently fired, you would be fine with either 1:7 or 1:9. I have also been told by reputable sources in law enforcement that 1:9 is recommended for plinking, and 1:7 for hunting and home defense.

To break it down, 1:7 will do just fine with shooting lighter and heavier rounds. 1:9, on the other hand, will handle lighter rounds better, and will not do so well with anything heavy at long distances. (Fig. 1a)

Carbine vs Mid-Length vs Rifle AR-15 - thearmsguide.com

A comparison photo of different length gas systems, barrels and rail systems for an AR-15. Image courtesy of laruetactical.com

Q: What does carbine, mid-length and rifle length mean when choosing a barrel?
A: It simply means where the gas port in the barrel is placed. It is also sometimes referred to as the “gas-system”. Carbine and mid-length gas systems tend to be on barrels of 16-18 inches and shorter, while barrels with a length of 20 inches and longer will have a rifle length gas system.

It is important to know what length gas system your barrel has because the gas tube you purchase will need to be the right length in order to fit properly. For example, you cannot fit a carbine length gas tube onto a barrel with a rifle length gas system. The gas tube will be too short.

Q: I am ready to build my AR-15 lower receiver but I do not know the steps. How do I do it?
A: Great question. In the following posts in this “How to Build an AR-15” series, I will go over how to build your AR-15 (starting with building your lower receiver, and moving from there to the AR-15 upper), what tools you will need, and I’ll offer some helpful tips along the way. Stay tuned.

About the Author

Nate Schultz is employed within the field of Law Enforcement, is an avid shooter, firearms enthusiast and hobbiest gunsmith. When he is not writing for The Arms Guide, he is producing content for his YouTube channel: www.youtube.com/nsz85


103 comments
adam marks
adam marks

Amen. Right back at cha brother....happy building. ..

auwillhunting9989
auwillhunting9989

Thanks, im sure I'll have questions!!!!! " God Bless Our Soldiers, Veterans, And The Ones That Gave All " ( Right To Bare Arms)!!!!

adam marks
adam marks

In my opinion, full stainless is reserved for the bull barrel reach out fuck someone up or match competition. If what you said is home defense and range , any good chrome lined barrel with the appropriate twist rate for your use will work just fine....and save you a ton of money. ......unless you plan on putting a M203 underneath it really doesn't matter. ...other than weight.

auwillhunting9989
auwillhunting9989

I won't to thank you on your web site, im going to build my own ar and didnt where and to begin, your site give alot of knowledge, Thanks!!!!

adam marks
adam marks

No problem. There are a lot of knowledgeable guys on this site. If you have any problems during your build or want to bounce ideas back and forth, feel free. Hope my answers helped you....good luck and have fun.

auwillhunting9989
auwillhunting9989

I've got question, I feel that the barrel type is really important, I fully understand what a ideal barrel to pick for my build. My question is, what is the difference in, stainless steel, stainless steel lined, or just a standard barrel that you get when you purchase a standard ar15? Im a hunter and home defense type of guy, what type of barrel would you recommend??

adam marks
adam marks

P.s. there is no stainless lined. It's full stainless or chrome lined, hamammered forge and fosghate coated .

adam marks
adam marks

Chrome lined is just fine. Unless you are going to reach out and f. Someine up or match competition, I would stay away from full stainless. Besides you'll save a ton of money. ..... benefits : less money, lightweight. All depends on twist rate desired and whether you plan on putting an M203 underneath.

Shuckins
Shuckins

Greetings Nate, et al.  I've become interested in building a minimalist Ar-15 around the 6.5 Grendel.  However, I've never built an Ar-15 before, and I'm uncertain about whether or not my tool skills are up to the task.  I have trouble manipulating small parts.  So, is it possible to buy fully completed upper and lower receivers, and a barrel, which my meager skills would allow me to just "snap together"?  The same sort of thing would apply to the collapsible butt-stock, etc.


Regards, Shuckins

adam marks
adam marks

Given your skill set, (no disrespect ) I would buy a complete upper in 6.5 , pick what lower you want. Have a gun smith or friend assemble said parts, i.e. dpms lower parts kit or whatever and I think you can handle the rest....that being the guns furniture and buffer tube assembly.

Shuckins
Shuckins

@adam marks 

Thanks Adam.  Any particular brand of upper receiver & barrel that you would care to recommend?

Regards

adam marks
adam marks

Spikes tactical makes some awesome barrels, but that's just what I put on my build. Daniel defence is another. Unless you have a vice, armors wrench, upper and lower receiver vice blocks and a torque wrench I would just buy a complete upper. Don't get me wrong though, with a small tool investment and several utube videos you can do the whole build your self. You're eventually going to have to completely break it down for through cleaning anyway and the satisfaction of completely building it yourself can't be beat. hope this helps.

Bill1943
Bill1943

I purchased a raw lower and it needs to be drilled, Where do I get directions for this?

adam marks
adam marks

Should have come with your 80% lower but the place you bought it or the Web is a good place to start.

Fishinsurf1969
Fishinsurf1969

I just want to make sure That I'm following all the laws. The last thing I would want would be to break any gun law that would have a negative impact on myself.


adam marks
adam marks

I hear ya. Start by finding out what your laws are first about building an ar in your state, as all laws about that vary state by state.

Fishinsurf1969
Fishinsurf1969

I'm considering building a AR. Am I understanding this right, The only time I'll have to fill out the paper work and follow the proper channels according to state law is when I purchase the lower receiver is that correct ?

adam marks
adam marks

I love in CA and if you know anything about an oppressed gun state, we're it....for us the only thing that needs to be registered is the lower...unless you buy a 80% lower and mill the rest out yourself. Then it doesn't need to be registered.

ThomasKarlmann
ThomasKarlmann

What does this mean: "Q: Do I need to be licensed or be a gunsmith to build my own AR-15?

A: Not unless you’re milling the lower receiver yourself."  If all I need is a drill press, and an 80% lower, what regulation is stating that I need to be "licensed" or somehow be a "gunsmith"?  Please explain.

KitBolton
KitBolton

No license needed. As long as you are building the AR for you, the law allows you to build at home. If you want to sell the AR you build using 80% lowers (no serial #'s) then you need to be licensed as a manufacturer. Anyone who can legally own an AR any other way (pass a background check at a gun shop) can legally buy and mill 80% lowers. The laws do not consider an 80% lower a finished part so it's not a gun part yet therefore no FFL needed to buy them.

adam marks
adam marks

No.ar 15 is up to 6.5, 6.8 and 50 beowulf.ar10 is 300 black out and 308 and the like.it's sorta similar to bolt action rifls......short action or long action, and the calibers that go along with such actions.

adam marks
adam marks

No.with the ar15 I believe that you can change out uppers to a maximum of 6.5 and 50 be wolf. Ar10 is a300 Blackout 308 platform.

adam marks
adam marks

For your first build I would stick to the ar15 platform regardless of what calibers you choose. ..i.e light to medium cartridge. Cheaper. ..a little. ...it's a relative term.but they both build the same way. If you have some mechanical skills and can follow directions and u tube videos you can build your upper and lower. Most people build their lower and then buy a complete upper.

adam marks
adam marks

But I think that's cheating. If you're going to do a build from scratch, then go the full Monty. .....much more satisfying when it's said and done!

adam marks
adam marks

Cool. I stand corrected. I thought the whole upper receiver needed to be changed out.

adam marks
adam marks

I need to amend a previous post. You can shoot up to 300 black out in the ar15 platform. Providing you change out the barrel of just swap out a complete upper.

tyfultongx
tyfultongx

@adam marks The 300 Blackout is built from the 5.56, so will function in the AR15.  It would only require a barrel change.  All other parts from an AR15 in 5.56 (or .223 Rem) will function, including the magazines and BCG.

adam marks
adam marks

You are correct. ...my bad......brain fart.

Jharris510
Jharris510

Can a 308 upper be put on a lower that has a 223upper?

Thanks,

Jh

adam marks
adam marks

No...only 300 black out because it uses a necked up 5.56 case...dimensions aren't favorable for a 308 case without changing the lower dimensions ergo...the ar 10 platform.

Travis08
Travis08

Im considering using a magtech magnesium lower for an ar 15 build have not heard much about the magnesium lowers how do they compare to a forged lower will I lose any strength,durability or reliability using magnesium lower.I really like the look but do not want to compromise performance.

Thanks

Travis P

adam marks
adam marks

I've heard about them as well but do not have any experience with them, sorry. ......utube it.

VVJoiner
VVJoiner

I want to get a kit for my thirteen year old son...WHAT DO I DO FIRST?  Besides the obvious....

adam marks
adam marks

I love your videos. I am building my first AR and have the complete lower including buffer assembly, stock and magazine. I have the upper with forward assist and dust cover installed. What's next? Cbg or barrel assembly.any suggestions?

exasperatus2002
exasperatus2002

great articles. I have an 80% polymer lower receiver that I have to mill out for an ar 15. It doesn't state what calibers it will handle. Do I have to go .223 or 5.56 will it handle 7.62 x 39 mm or .308 provided that Im using the appropriate upper receiver for the caliber I want to use?

chyldeorchid
chyldeorchid

You'll have to go with .223/5.56, you would need an AR10 receiver to chamber 7.62

DrewFire
DrewFire

Just want to give a big thanks to you. 

This helped me a lot to start my AR15 build 

and gave me a huge insight of what I need 

and what I should look for.

Thank you again.

- Andrew 

Nate Schultz
Nate Schultz

@palmer It sure looks like it to me, but that is also an 80% lower receiver so you will need a jig and a mill or a machine shop nearby.

42Coop42
42Coop42

I am new to ARs'.. Can I use a model 1 sales 6.8 SPC upper half and put it on a stag arms 6.8 SPC lower half? Will this work, or do both halves need to be the same brand?

Nate Schultz
Nate Schultz

@42Coop42 The upper and lower receivers do not have to be from the same manufacturer. Typically, if they are from the same manufacturer, the fit will be better but as long as they are in spec, you should be just fine.

JimmyChadwick
JimmyChadwick

I have completed my AR 15 lower. What are the initial steps that should be taken to start the upper? 

Nate Schultz
Nate Schultz

@JimmyChadwick I have an entire series of articles covering how to build an AR-15 from start to finish. You will just have to search this site for what you are looking for :)

thederdog
thederdog

Thanks, can I build a AR-10 in the same fashion as a AR-15 ?

Nate Schultz
Nate Schultz

@thederdog I have not built an AR-10 style rifle yet so I cannot tell you for sure one way or another. Sorry :(

thederdog
thederdog

Already completed the lower for my AR-10. Pretty much the same as a AR-15.

thederdog
thederdog

Is there a AR-15 built in 7.62

JunkfoodZombie
JunkfoodZombie

Which 7.62?

7.62x39? Yes, but not all that common.

7.62x51? Yes, that would be the AR-10 platform.

thederdog
thederdog

Can I build a AR-10 in the same fashion as a AR-15

thederdog
thederdog

In the 7.62x51, what twist would you suggest. I have been a pistol guy most of my life. Moved to Washington and now am starting to see a need for rifles. Purchased my first rifle (Winchester 30/30) a few weeks ago and have enjoyed it more than I thought iwould. So I am pretty green with my knowledge on rifles

JunkfoodZombie
JunkfoodZombie

Depends on what weight bullets you plan on shooting. A 1:12 twist is good for 170 grains and below. A 1:10 is better for heavier bullets and 1:11 is a good compromise. Any twist will shoot any weight but each twist is going to shoot certain weights more accurately than others. I would suggest doing some research to see which twist is best for the bullets you plan on shooting. Good luck!

P.S. .30-30 rules!

thederdog
thederdog

Thanks a ton, really appreciate your help.

JunkfoodZombie
JunkfoodZombie

Any time. You can check out my YouTube channel. It's JunkfoodZombie. (One word). I try to put a variety of stuff on there and much of it is geared towards helping other people. Good luck with the build!

thederdog
thederdog

Thanks, just got my AR-10 lower, and colt trigger. Upper is on it's way. Appreciate everyone's help

JunkfoodZombie
JunkfoodZombie

Yeah. It's basically the same rifle with sime larger parts. 7.62x51 was the original caliber for the M16 platform, It was the AR-10 first. It was quickly changed to accomodate the 5.56x45 round and dubbed the AR-15, then the M16.

adam marks
adam marks

The closest you'll get is 300 black out. Basically your 308 bullet in a 5.56 case.

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