III. Firearm Information by Type

D. Rifles

2. Rifle Reviews

b. Self-Loading Rifles

12. AR-15
1. How to Build an AR-15
by Julian Macassey (julian@tele.com)

The description on headspace for the AR-15 is written by Chris J. Pikus (cjp@megatek.com)

	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 Viet Nam 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 realise 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 Viet Nam. 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
S.A.S.E.

	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 (Aluminium) (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 fiddly
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 "fiddly" 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 kersosine 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, 5.56.mm M16A2 W/E

(1005-01-128-9936)

"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

Headspacing

	The description on headspace for the AR-15 is written by
cjp@megatek.com (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.

	 _______________________
	|			\
	|			 \_____
	|
	|)			
	|			  _____
	|			 /
	|_______________________/

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

	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 
concerned.

	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
gauge too. BUT ABSOLUTELY, UNDER NO CIRCUMSTANCES SHOULD A BOLT CLOSE ON
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.