How to Build an AR-15

        The AR-15 is the semi-auto civilian version of the military M16

battle rifle.

        Since its introduction in the nineteen-sixties, this rifle has

been issued to several armies and is still the standard issue weapon

of the U.S. Army and the U.S. Marines. It fires a round known as 5.56

mm NATO or Winchester .223.

        This rifle was originally designed by Eugene Stoner when he

worked for the Armalite Corporation in Southern California. The rifle

went in to production at Colt's facility. 

        The rifle and parts for it have been produced by many

companies. During the Vietnam era, it was even produced by the

Hydrostatic division of General Motors. 

        As this is a U.S. basically a U.S. military device, parts and

documentation are freely available on the surplus market. 

        The easy availability of parts and the simplicity of the gun

make it a cheap and effective rifle. The gun, in all it's various

configurations can be purchased ready made, or assembled at home with 

simple tools. 

        People assemble their own rifles for several reasons. Most do

it to save money. Some do it learn the mechanics of the rifle. Many do

it because they have accumulated parts at gun shows and realize they

are just a few parts short of a second rifle. Some build their own

rifle to be able assemble a custom unit that has the kind of barrel

and stock that they want.

        What follows is a list of documents and parts supplier that

will enable anyone who has some mechanical skills to assemble, repair

or replace parts on an AR-15.

        Legal Note: It is illegal for a civilian to own a full

auto or select fire M16. The AR-15 is a semi-automatic only version.

The difference between the two rifles is in the bolt, sear and safety

mechanism. As a general rule the parts sold to civilians are the

semi-auto bolt and safety. But tales have been told of M16 bolts

ending up on the surplus market. 

Documents and Guides

        If you are planning to do any work on an AR-15, the best help

is the Video available from Quality Parts. It costs $20.00 and shows

techniques and tools. 

        There are also manuals and guides available. Some are U.S.

military documents and some civilian books. Below is a listing and a

list of suppliers:

        From the Government there is the "Technical Manual". This 

covers repair, adjustment and use of special tools. Lots of people 

sell this one. Of course the Marines and the Army have different 

versions of the same book. Also there are M16 A1 versions out there 

as well as A2.

Here are the government numbers for this one:

U.S. Army           TM 9-1005-319-23&P

U.S. Air Force      TO 11W3-5-5-42

U.S. Marine Corps   TM 05538C-23&P/2

"Technical Manual  Unit and Direct Support Maintenance Manual

(Including Repair Parts and Special Tools List"

This is available from Sierra Supply, Quality Parts, Tapco, Lone Star

Ordinance, L.L. Baston and no doubt others. 

        Note the numbers above may vary a digit or two depending on

which edition you buy. The title will remain the same though.

        There is another book, which looks like it was a cut and paste

job from a government manual. 

AR-15, M16 Assault Rifle Handbook. Edited by J. David MacFarland.

Firepower Publications  El Dorado AR 71730

        Another Book is "The AR-15/M16 - A Practical Guide" by Duncan

Long. Paladin Press, Boulder, Colorado.

        Below is a list of companies that should have what you need.

Lone Star                               (800) 482-3733 (512) 681-9280

L.L. Baston                             (800) 643-1564 (501) 863-5659

Sherwood International                  (818) 349-7600 (800) 423-5237

Quality Parts                           (207) 892-2005 (800) 998-7928

TAPCO                                   (800) 359-6195

Sierra Supply                           (303) 259-1822

Sierra Supply has the best selection of books.

        For history etc, read: "The Black

Rifle", Jane's Infantry Weapons, and Small Arms of the World.

What To Build


        There are several variations of the AR-15. The two greatest

variations are the A1 and A2 types. The A1 has a triangular handguard

and no elevation adjustment on the rear sight. These are the guns you

will see pictures of in books about Vietnam. The A2 version has a

round handguard and an elevation wheel on the rear sight. There are

other differences between the two guns such as stock length. But these

are the differences which can be seen from a distance. The pistol grip

is also different between the A1 and A2 versions. Reading the

books mentioned above will give more detail on the differences.

        The barrels are available in several lengths and twists. There

is also the HBAR - This is a "Heavy Barrel", which means it is less

prone to bending. The twists available are 1:7, 1:9 and 1:12. The 1:7

is the current military standard and is designed for the heavier

bullet. The 1:12 is the original twist and was designed for the 55

grain bullet. The 1:9 twist is a compromise between the two. The other

barrel option is chrome plating. Accuracy buffs will say that a plated

barrel is not as accurate as a regular steel barrel as plating is

never uniform. The advantage of chrome plating is a more rugged barrel

that is resistant to rust and wear.

        Barrel lengths available are: 10, 11.5, 14, 16, 20, 24 and 26

Inches. The legal minimum for a rifle barrel is 16 Ins, so if you buy

a barrel shorter than 16 Ins, it needs to have a long flash suppressor

brazed on to it so it meet the 16 Ins minimum required by U.S. law. 

        All of these options are explained in the various catalogs of

the companies supplying parts.

        The standard stock is the nylon rifle stock with a trap door

in the butt. The other stock is the Telescoping butt stock. This stock

with a 16 Ins barrel makes a nice carbine often referred to as a

"shorty" or CAR-15.

        There is also an option on the pistol grip. Lone Star

Ordinance sells a pistol grip with a trap door. This grip is available

in A1 or A2 styles.

        Looking over the catalogues (see end of this article for a

list) will give you an idea of what you may want and what it will

cost. Then you may order the parts.

The Lower Receiver

        The part that has the serial number on it is the Lower

Receiver. This is the only part that can not be bought without

paperwork via mail or at gun shows. To purchase a lower receiver, you

need to be a Licensed firearms dealer (FFL) or carry out your

transaction via an FFL. There are some FFLs on the net. Also Shotgun

News will send you a list of FFLs if you send them a dollar and an


        You can make as many barrel/upper receiver assemblies as you

like and swap the lower receiver between them. This can give you

several rifles. The top and bottom parts of all AR-15s will break

apart and are interchangeable.


Special Tools

        You can assemble an AR-15 with a well stocked tool box and

some patience. But to do the job well with the minimum of frustration,

you should use the special tools. You can buy your own tools or you

can borrow tools from someone who has already assembled a rifle.

Remember, if you borrow tools, you have to return them immediately.

Having someone nearby who has assembled a rifle is helpful. 

        Here is a list of tools:

        Drift Punches

        Barrel Wrench (Handy for all AR-15 Owners)


        Vice Jaw Blocks (Aluminum) (You can make out wood)

        Telestock Wrench (Handy for assembling the Telestock)   

        Sight Adjustment Tool (For adjusting the sights)

        Headspace Gauges (For checking Headspace)

        Sleigh Punches (No one I know sells these - make your own)


        You can buy kits from Quality Parts, Lone Star Ordinance 

and others. At a minimum, you need to buy the Headspace gauges and the

barrel wrench. Everything else a well stocked workshop will have or

will be able to make. The sleigh punches are shown on the Quality

Parts video. They can be made out of brass rod with the aid of a

drill press. They are used to push in the roll pins. The AR-15 is

pretty much held together with roll pins. You can put the roll pins in

with a pair of needle nose vice grips and a small ball peen hammer.

After you have put two in the hard way, you will take a break and make

the sleigh punches. Besides the special sleigh punches, you can use

nipple punches, they will work, but are still not as good as the

sleigh punches.

        Getting the front detent pin in the lower receiver can be a

trial. This is a pin and a spring that holds the front push pin in

place. Brownells sell a special tool for this. You can use a knife

blade to do this. It is the most tricky part of the whole assembly.

        Putting together an AR-15 pretty much consists of pushing in

roll pins and inserting compressed coil springs. These are fiddle

parts that can fly across the room, only to be found when they get

eaten by pets or jam the vacuum cleaner. It is a good plan to place a

white bedsheet under and around the workbench when assembling. You

should wear safety glasses when building the rifle so a spring will

not head damage your eyes. If you loose a thirty cent spring, you 

will have to put the whole assembly on hold while you wait for 

the part to arrive.

        Note also that all the "fiddle" parts are not marked, numbered

or otherwise identified. You will have to identify them yourself

during assembly. It is a good idea to tip the parts onto a white

dinner plate or into a white plastic egg tray. The egg tray will allow

you to separate the parts into springs, pins etc.

Quality Checks on a Completed Rifle


        When you have finally assembled the rifle, the next step is to

check your work. Remember you are assembling a piece of machinery

that could be dangerous if it malfunctions. Go over the rifle and make

sure that all parts are correct and tight. Check assemblies with the

drawing supplied with the Technical Manuals. 

        Before you fire the rifle, check the headspace using a set of

headspace gauges. The correct use of headspace gauges is explained in

the Quality Parts video. If your rifle is not headspaced correctly,

contact the company that supplied your barrel and bolt, or take it to

competent gun smith who knows what to do. If you know how to adjust

the headspace, you don't need to read this document. But should you be

doing so, Quality Parts sells reamers for the AR-15. Note that the

headspace check is mostly a safety check, chances are everything will

be OK. At the end of this description is a description the purpose and

process of headspace checking. Military barrels are chrome plated, it

is believed that reaming a these barrels is not possible because of

the risk of flaking chrome. If you have any doubts or questions, call

the supplier of your barrel and bolt.

        The rifle should be cleaned before firing. The barrel is

liable to have a coating of heavy grease inside it. This can be

removed with solvents such as kerosene or mineral spirits (Turpentine

substitute - paint thinner) and a proprietary gun cleaner such as 

Hoppes. Pass patches through the gun until they come out clean.

        If all the visual tests pass, then it is a good idea to load a

couple of dummy rounds (Snap Caps) into a magazine and manually feed

them through the rifle using the charging handle to feed them. Check

that the safety works - it will only engage when the rifle is cocked

- and that the rounds are ejected when the bolt travels back.

        The final test is at a range. Pointing the gun at a solid

backstop, a target is not needed yet as you are not adjusting the

sights, load one round in a magazine. Insert the magazine into the

rifle and feed it into the chamber. Pull the trigger and make sure

that the rifle fires and ejects the shell. With only one round in the

chamber, the bolt should be held back by the follower in the magazine.

Now load two rounds and repeat. This test ensures that the rifle is

feeding and firing properly. Finally insert 5 rounds. Take careful

note that each time the trigger is pulled only one round fires. With a

new rifle, there may be some ejection problems. These can be caused by

a rough and sticky chamber or bad lips on the bolt face. Check by

carefully hand cycling dummy rounds. If the return spring is not

strong enough, the rifle will cycle by hand, but will tend to fail to

feed in semi-auto use. Try another return spring.

        To sight in the rifle and learn how to clean and care for it,

you should read the manual:

U.S. Marine Corps TM 05538C-10/1A

U.S. Army         TM9-1005-319-10

Rifle, M16A2 W/E


"Operator's Manual W/Components List"

This is available from Sierra Supply.

Parts Suppliers

        Below is a list of companies that sell parts for AR-15s. Some

of these companies also sell whole guns.

        Don't forget also that gun shows will also have parts. 

        In no particular order, here is a list of suppliers. I have

called all of them. 

Amherst Arms                            (301) 829-9544

DPMS                                    (800) 578-3767

Eagle Arms Inc.                          (309) 799-5619

Essential Arms Co.                       (318) 566-2230

Gun Parts (Numrich Arms)                (914) 679-2417

L&G Weaponry                            (714) 840-3772

L.L. Baston                             (800) 643-1564 (501) 863-5659

Lone Star Ordinance                     (800) 482-3733 (512) 681-9280

Nesard                                  (708) 381-7629

Olympic Arms                            (206) 459-7940

Pac West Arms                           (206) 438-3983

Quality Parts                           (207) 892-2005 (800) 998-7928

Rock Island                             (309) 944-5739

Sarco Inc.                               (908) 647-3800

Sherwood International                  (818) 349-7600 (800) 423-5237

Brownells also sell special tools for AR-15s  (515) 623-5401


        The description on headspace for the AR-15 is written by

[email protected] (Chris J. Pikus)

        Headspace is that measurement describing the size of the chamber on

a barrel. In the case of rimless rifle cartridges, it is the distance from

some arbitrary point on the case neck taper back to the bolt face. Here is

a crude ASCII drawing.


        |                       \

        |                        \_____



        |                         _____

        |                        /


        | <--------------------> |


        In the more general case (e.g. pistol, rimfire, rimmed cases, and

belted magnums), you can imagine headspace as measured from whatever the

cartridge rests against on the front of the chamber all the way back to the

bolt face.

        These numbers are specified for each cartridge by the Sporting Arms

and Ammunition Manufacturers Institute (SAAMI) and it's important to have this

 measurement fall within SAAMI specified tolerances. 

        Too small, and you may not be able to close the bolt on some

ammunition that's on the large side of its tolerance range. Worse yet, it

will close and let you fire. Firing ammunition in a chamber that's too tight

leads to dangerously high pressures.

        Too large a chamber, and there's lots of room for the cartridge

to rattle around in there -- well not really. What happens is that the

brass casing can rupture and 55,000 psi hot gases start rushing out in

every which direction, including at your precious body parts. Think of the

high pressure gases that force a bullet down the barrel finding other

avenues of escape. This is what some people mean by "the gun blew up on me".

One sign that this is  going to happen soon is that the backs of your brass

casings start looking like someone took a sledge hammer to them and flattened

out the primers and lettering. This is because the casing is literally being

hammered against the bolt face.

        So that's headspace, and why it's important. But what are all these

gauges about? The look like little steel cartridges without the bullets.

You stick them into the chamber and try to close the bolt. Whether the bolt

closes or not -- and whether that's good or bad -- depends upon which gauge

you're trying to use.

        The Go gauge measures whether it's too small. It's made just

a teeny bit smaller than the minimum requires chamber size. If you cannot

get the bolt to close on the "go" gauge, then the chamber is too small.

Thus, if you can close the bolt, it's a "GO" as far as chamber size is 


        The No-Go measures whether the chamber is too large. It's made 

just a bit larger than the factory tolerance chamber size. You're not

supposed to be able to close the bolt on these; if you can, then the chamber

is too large. Thus, if you can close the bolt, it's a "No-Go" on the barrel/

bolt combination.

        So much for the GO and NO-GO gauges: what about the "Field" gauge?

Well, the GO/NO-GO measure the SAAMI specs for *factory* tolerances for

newly chambered rifles. The field gauge checks the end-of-life tolerance

for a chamber. If you're familiar with manufacturing machinery, you may be

aware of two sets of tolerance specs: the factory tolerance for when

something is new, and a more generous end-of-life spec for when to throw

something away. So is the case here.

        Fortunately, since the wear mechanism for a firearm chamber is to

stretch, we only have to worry about the dimension beyond the NO-GO mea-

surement; which is our "field" gauge. The field gauge is sized to be the

largest acceptable headspace possible. If you can close the bolt on the

field gauge, then the barrel is worn out and it's time to replace it. To

continue shooting it is dangerous.

        In theory, the bolt of a well used rifle will close on a NO-GO


A "FIELD" GAUGE. That's when you take the gun back for rebarrelling.

        Personally, when I've bought really old guns, they closed on the

NO-GO gauge, but not the field gauge. That's acceptable for me. I know not

to shoot really hot ammo through it, and that the accuracy suffers because

of the large chamber. I keep them for the historical value, but I could

rebarrel them back to factory size if I wanted to.

        Since you've got a new gun (with less than 10,000 rounds through it),

I would suggest you buy both a GO and a NO-GO gauge. Play it conservative,

check the headspace every few thousand rounds and don't go beyond the NO-GO.

As you know, most people don't even bother with that but I like to play it 

real safe.

        Basic rules....

    For a new gun:

        a. Closes on the go gauge

        b. doesn't close on the no-go gauge

    For an old rifle that's been rode hard and put up wet:

        a. closes on the go gauge

        b. probably closes on the no-go gauge

        c. definitely does NOT close on the field gauge

        It's cheap insurance to have a set around for every rifle you have,

especially if you shoot a lot. Plus if you change around bolts and/or barrels

like you plan to you have to_ check each combination because each setup could

vary a few thousandths between them. (fortunately you only have to do it 

when you first introduce them to each other. And every few thousand rounds

if you wish.)

        You can get your very own set by calling Brownells at 515-623-5401

and ordering at least the GO (part #319-223-464), and the NO-GO (#319-223-467)

for $16.00 each. The field gauge you can buy later if you wish (#319-223-470).

Don't forget to ask for their catalog; it's an education all by itself.

Headspace gauges are also sold by Quality Parts.

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