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1. Introduction
2. Getting Started
3. Lower Receiver Assembly
4. Upper Receiver Assembly
5. How To Change A Barrel
6. How To Install A Free Float Fore-End Tube
7. How To Properly Sight In your New AR-15
8. Where To Buy Parts For Your Rifle
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1. Lower Receiver Assembly
Building a complete lower receiver from a stripped lower receiver.
This section will take you step-by-step through the process of
assembling a lower receiver from a stripped receiver. The whole
process, from start to finish, should take around 30min to an hour....
depending on your skill level. As to the skills needed for assembling a
lower receiver…If you can poke small objects into small holes, then
you can build your own receiver.
Parts Needed:
1. Stripped Lower Receiver
2. Lower Parts Kit (contains the trigger grip and all other parts to
complete the lower)*
*Note – The LPK contains all the parts needed to build a standard
rifle, however all the parts can be substituted for other aftermarket
parts. The most commonly substituted parts in the LPK are the grip
and the trigger. If you want to assemble your rifle without using a
pre packaged LPK, that’s fine, just make sure you have all the
needed components. (use the labeled picture below as a guide for
what you need)
Required Tools:
Honestly... there are NO special tools necessary. Some will argue its
good to have roll pin holder tools, roll pin punches, etc. After namy
years of building rifles, I now have all those tools and I still hardly
ever use them. The only tools I feel are really necessary are a small
brass punch and light hammer. As A way to reduce scratches I would
also recommend you have a roll of masking tape and or electrical
tape to protect the receivers finish. Everything else can be
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Lower Receiver Assembly Instructions:
There is not really a special order you have to go in. Common sense
will tell you some things have to be put in first, before others... but
for the most part its not really important. The order shown here is
the most common order of assembly as well as the most straight
forward. Nothing goofy here.
Stripped Lower Receiver
Here is the parts list that comes with a lower parts kit....
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Here breakdown of the parts included in the Lower Parts Kit. These
are all the components you will need to build your Lower Receiver.
Here is a diagram of the trigger group and how to correctly assemble
it. The trigger group is easy to assemble incorrectly so use this
picture as a guide.
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1. Insert the mag-catch (part with threaded post) on the left side of
the receiver (side with the serial number and all the writing) and then
install the mag-catch spring from the right side.
Then, grab the mag-catch button and push it towards the magcatch. Then, spin the mag-catch (left side) to tighten it. Stop when
the mag-catch threaded post is flush or nearly flush with the
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2. Next is the bolt-catch. Get some masking tape and cover the
lower receiver here: This is to keep us from accidentally scratching
the lower receiver as we tap in the bolt-catch roll pin into place.
Insert the roll pin, and tap lightly to get it started... but do NOT tap
it all the way in yet. Insert the bolt-catch spring and buffer, with
the spring in first and the buffer facing out:
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Then, install the bolt-catch, holding spring tension on the plunger,
while aligning the hole in the bolt-release with the roll pin hole in
the lower.... and using a punch, tap the roll pin all the way in. If you
want to avoid marring the finish, place more tape over the roll pin
area as it gets close to flush to drive it all the way home. The boltrelease only fits in one direction, so you will have no trouble figuring
out how it should go.
3. Now we’ll install the front pivot pin. Some people have trouble
with this one, as it’s very easy to accidentally launch the detent
across the room. Just be careful, and take your time and you won’t
have a problem. Insert the spring into the detent hole:
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Then insert the detent. It will barely even start in the hole before
you really have to push for all the spring pressure. Then, using the
front pivot pin, push the detent back while you insert the front
pivot pin into it's hole in the receiver. Once the front pivot pin is
in far enough the detent will snap out into the groove on the pivot
pin and hold it on place
4. Install the trigger guard. This is pretty straightforward. Insert
the trigger guard with single hole side in the receiver. Then align
the roll pin hole up with the hole in the "ears" of the receiver. BE
VERY CAREFUL HERE. You must support the "ears" on the
bottom side if you tap the roll pin in place. If you don’t support
the bottom ear, you could break it off when tapping the pin in place.
Also, some roll pins and/or trigger guards are out of spec. If it takes
what you think is too much force, or starts to deform your roll pin,
STOP. If this happens, see the end of this section for an alternative
method of installing roll pins pin by squeezing the pin in place.
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5. Drop the trigger and trigger spring assembly into the receiver
(refer to the above trigger group diagram for how it should look).
Then push the disconnector on the top of the trigger, with the
notch in the disconnector over the coil spring in the top of the
trigger. Then using a trigger pin, insert it through the lower
receiver... into the trigger, through the disconnector, and back into
the other end of the receiver. This takes a lot of wiggling to get it
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through... but be patient and you can do it!
6. Next, grab the hammer/hammer spring assembly, and insert
it in the lower. The two long legs of the hammer spring should rest
on the top of the trigger pin installed in step 5. There is quite a bit
of hammer spring tension... but squeeze the hammer into the
receiver so that the hammer pin hole lines up with the holes in the
lower receiver, and install the hammer pin. You might have to tap
lightly to get the pin through the hammer, but just LIGHTLY. Then
cock the hammer.
7. Next, install the safety selector into the left side of the receiver.
Install the selector detent, & spring into the detent hole:
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Install the pistol grip and grip screw, taking care to ensure the
selector spring goes into the hole in the grip. Don’t Pinch the
8. Rear takedown pin: Install the detent and then the spring...
and the takedown pin into the rear of the receiver. The stock will
hold tension on this spring/detent, when it is installed, next:
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9. Thread the rifle or carbine buffer tube slowly into the receiver...
taking care not to damage or lose the takedown pin spring. The
buffer tube should be threaded in just up to the buffer hole.... and
then insert the buffer stop pin and spring:
Then thread the tube a little more, so that it holds the buffer stop
pin in place, but does not touch the center part of the pin and bind
its movement:
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Then tighten the stock in place... Pictured is a carbine stock. You can
use the CAR wrench for the castle nut (shown) or the CAR nut....
and some people like to add a little blue loctite to this nut so it won’t
back off in the field: NOTE - you may not wish to use Loctite. It is
not required. Especially if you think you might be taking it apart
again soon. Loctite just helps assure it won’t get loose on you while
shooting, and some people never have a problem with this. If you do
decide to use Locktite, only use a drop or two and it will break loose
pretty easily when you need it to.
The CAR wrench for the newer castle nuts is a good tool to have. You
can get it here:
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Now, just insert the carbine or rifle buffer and spring. Cock the
hammer back to make this easy. The spring goes in first, with
the buffer going in next. Push the buffer in past the buffer pin
sticking up.
You are all done! Perform a trigger mechanism safety check to see
that everything is working, then your lower receiver is ready to go.
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DO NOT DRY FIRE A LOWER. Dry firing of the assembled weapon
is fine. However, if you allow the hammer to drop on a lower that
does not have an upper installed, it will potentially damage the lower
receiver. The hammer will strike the bolt catch, which will damage
the bolt catch receiver area and pin. If you do it a couple times it will
be fine... but continued dropping of the hammer will likely result in
damaging the bolt catch, receiver, or both.
Alternative Method of Installing Roll Pins
As an alternative to driving pins in with punches, you can press them
in using vise grips or pliers. You will need needle nose pliers, vise
grips, and oil or grease to lube the holes.
Use large Vise Grip pliers, with the jaws taped with
masking or electrical tape to protect the receiver from
scratches. Adjusting the pliers so that they just barely
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press the pin in with the handles all the way together
gives maximum mechanical advantage:
Get the pin started in, and put in the spring, detent, and
position the bolt catch:
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Continue pressing in the pin by opening the pliers, turning
the knob 1/2 turn at a time, and pressing the pin in little
by little:
Now the pin is almost all the way in, it can be tapped in
flush with a few light taps on a punch or an ordinary
carpenters nail set:
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Now let's do the trigger guard:
Hook the trigger guard in the front, by the mag well, and
swing into position. If you don't have the trigger guard in
position when you try to start the pin, it will break off the
tab of your expensive lower:
Press in as in previous post, turning the knob of the Vise
Grip 1/2 turn at a time:
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Now that you have it this far, finish by tapping in flush
using punch or nail set:
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Common Lower Assembly Questions &
Do any of the lower receiver parts need to lubed?
CLP is all you *need* for any part on the AR15/M16 rifle.... and at a
minimum should wipe down the FCG, safety, and pins, with CLP.
That being said, on initial assembly, I like to use a little moly-grease
on the sear engagement surfaces on the trigger and hammer, and
inside the trigger and hammer pin holes. I place a dab of grease on
the new pins, and work them in and out to lube the inside of the new
fire control group. I also add a dab of grease to the safety selector,
and takedown/pivot pins.
Do you ever find the trigger and hammer pin move, or are
they held in place fairly well? I’ve seen some locking pins,
are they necessary?
If the fire control group is installed correctly.... there will be no
movement of the pins. There is a "j" hook installed in the hammer
that firmly holds the hammer pin in place so it cannot move. Then,
when the hammer is installed, one of the legs of the spring rest in
the groove on the trigger pin, so that one cannot move. I don’t see
the real use of "anti-walk" pins unless you are running some sort of
custom trigger that does not have these designs in place. Or, if you
do not want the pins to rotate in the receiver, you can install
oversized pins like in the RRA triggers, or a KNS pin set which locks
them from moving sideway or rotating.
Any grease necessary on the buffer spring?
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NO!!! A light wipe with CLP is all you need. NO GREASE on the buffer
tube! That SPROING noise is NORMAL, and is a good thing. When
you hear the noise change, that lets you know you need a fresh mag.
My bolt catch is sticky. My bolt won’t lock back or it is VERY
hard to release. Is this normal?
NO!!! This is a common issue with new parts. The hole in the bolt
catch should be large enough to easily allow the bolt catch roll pin to
pass through. If it does not, then the bolt catch hole is out of spec.
You can contact the vendor and have it replaced, or you can ream it
out larger with a tiny drill or grinding bit in a Dremel, or very small
round needle file. This is a cast hardened part, and does not drill
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4. Upper Receiver Assembly Instructions
Building a stripped upper receiver into a fully assembled upper
The upper receiver is the next part of the rifle we will assemble. It
just like the lower receiver should take around 3omin to build.
While this guide will walk you through assembling a upper receiver
from scratch. Many builders will skip this step and buy completed
upper receivers in their chosen configuration. Often times the price
difference in doing this is minimal.
There are a number of reputable companies who are now offering
complete upper receiver assemblies including the barrel for prices
that can sometimes make building it yourself not worthwhile, except
for the enjoyment factor (that can’t be replaced).
Required Tools:
All you will need to assemble your upper is a brash punch, hammer
and a gunsmiths bench block. You can get by without the block, it
just makes it easier.
Required Parts:
1. Stripped Upper Receiver
2. Upper Receiver Parts Kit
3. Bolt and Bolt assembly
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Upper Receiver and Parts (without barrel assembly)
1. Install Forward Assist Assembly on Upper Receiver. Slide the
forward assist spring onto the forward assist.
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Use your hammer to start the forward assist roll pin into the hole
on the bottom of the upper receiver. Only tap it in enough so that it
can stand on its own.
Insert the Forward Assist Assembly, make sure the pawl is
oriented toward the middle of the receiver (see picture - if you take
off the spring, you can see a flat side on the Forward Assist - this is
where the pin rides).
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While compressing the Forward Assist Assembly, drive the pin
through until it is flush with the receiver. Once the pin is firmly
started, you should not have to hold the forward assist in place and
you can use a large brass punch to drive the pin in until it is barely
sticking up. If you find this too awkward, you can use a small punch
as a slave pin to keep the Forward Assist Assembly compressed
so you can use both hands. You may have to take a small punch and
drive the pin a bit further until it is flush or even slightly recessed
(just look at both sides to try and center the pin in the Upper
Test the Forward Assist to make sure it moves freely in and out when
2. Install Ejection Port Cover Assembly on Upper Receiver. This
assembly consists of the Ejection Port Cover, Ejection Port Cover Pin,
Ejection Port Cover Pin Snap Ring and Ejection Port Cover Spring.
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Gently hammer Ejection Port Cover Pin Snap Ring the Ejection
Port Cover Pin. Be sure to make a direct, downward strike on the
snap ring. If you hit it off center, the Ejection Port Cover Pin Snap
Ring may fly across the room.
Lay the Upper Receiver on its side so the Ejection Port is facing up
and the Barrel Threads are pointing to the right as you stand over
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the Upper Receiver. Barely start the Ejection Cover Pin so it stays
in place on its own, making sure the end without the snap ring is
started first.
Place the Ejection Port Cover on the Upper Receiver in the open
position, making sure the holes in Ejection Port Cover are lined up
with the holes on the Upper Receiver.
Slide the Ejection Port Cover Pin through the hole in the Upper
Receiver that is closest to the Barrel Threads, stopping just before
the pin emerges in the middle opening of the Ejection Port Cover
(this is where the Ejection Port Cover Spring goes).
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While Holding the Ejection Port Cover Spring in your left hand (by
the end with the short part of the spring sticking out), grab the long
part of the spring that sticks out and wind it 1/2 revolution away
from your body, stopping when the long part of the spring is pointing
toward you.
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As you hold the spring under tension, place the long end on the right
side of the Ejection Port Cover (closest to the Ejection Port
Cover Pin that is part way through the assembly), while still holding
on with your left hand, and slide the Ejection Port Cover Pin the
rest of the way through, until the Ejection Port Cover Pin Snap
Ring stops your progress.
Close the Ejection Port Cover, making sure it snaps shut.
Reach inside the Upper Receiver and push the Ejection Port Cover
with your finger, making sure it snaps open.
Ejection Port Assembly is now installed.
3. Assemble Bolt Carrier Assembly. The Bolt Carrier Assembly
consists of the Bolt, Bolt Carrier, Bolt Cam Pin, Firing Pin and Firing
Pin Retaining Pin.
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Push the bolt all the way into the end of the Bolt Carrier; making
sure the large hole through the middle of the bolt is aligned with the
hole directly under the Bolt Carrier Key (hollow tube that is
attached by two screws to the Bolt Carrier). Make sure the bolt is
positioned so that the extractor is on the left side of the bolt when
looking at the bolt face.
Insert the Bolt Cam Pin through the large hole in the Bolt Carrier
(just under the Bolt Carrier Key). The holes in the Bolt Cam Pin will
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need to be perpendicular to the Bolt Carrier Key in order for the
Bolt Cam Pin to clear the Bolt Carrier Key for insertion. If the
Bolt Cam Pin will not go into the bolt, check the bolt orientation, as
it may need to be rotated 180 degrees. Once the Bolt Cam Pin is
inserted, rotate the Bolt Cam Pin ¼ turn so the large holes in the
Bolt Cam Pin are lined up with the front and back of the Bolt
Carrier and the Firing Pin can slide through.
Slide the Firing Pin through the Bolt Carrier (toward the Bolt)
until it stops.
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Insert the Firing Pin Retaining Pin through the Bolt Carrier
making sure the round end of the pin is nestled all the way into the
large recessed side of the Bolt Carrier. Since the Bolt Carrier is
hollow, the Firing Pin Retaining Pin needs to go through the
hollow part of the inside of the Bolt Carrier and enter the hole on
the other side before it emerges on the other side. It can be a little
tricky to achieve this alignment and pounding on the pin will not
help. Once in proper alignment, this pin should slide in easily.
Test the bolt to make sure it moves in and out of the Bolt Carrier
Bolt Carrier Assembly is now completed.
4. Assemble Charging Handle Assembly. The Charging Handle
Assembly consists of the Charging Handle, Charging Handle Latch
Spring, Charging Handle Latch Roll Pin and Charging Handle Latch.
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Insert Charging Handle Latch Spring into Charging Handle.
Start the Charging Handle Latch Roll Pin into the top of the
Charging Handle so it stands on its own.
While compressing the Charging Handle Latch into the Charging
Handle, line up the holes and drive the Charging Handle Latch
Roll Pin until it is flush.
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Charging Handle Assembly is now completed.
5. Install Charging Handle Assembly and Bolt Carrier Assembly
into Upper Receiver. To complete the assembly of the Upper
Receiver, you can go ahead and install these parts to ensure proper
fit. However, you will have to remove these parts to continue with
the installation of the Barrel Assembly.
Turn the Upper Receiver upside down so that the Picatinny rail is
against the work surface. Insert the Charging Handle Assembly
by lining up the tabs on the Charging Handle with the grooves
inside the Upper Receiver.
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Slide the Charging Handle Assembly in only far enough that it will
stay stationary on its own. Pull Bolt out of Bolt Carrier as far as it
will go so the Bolt Cam Pin will not contact the inside of the Upper
Receiver. The Bolt Carrier Assembly will not go into the Upper
Receiver if the Bolt is not pulled out.
Insert the Bolt Carrier Assembly (with the bolt face pointing
toward the barrel threads) into the Charging Handle Assembly so
that the Bolt Carrier Key rides in the trough on the underside of
the Charging Handle, stopping when the Bolt Carrier Assembly
and the Charging Handle Assembly are parallel and even with
each other.
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Push the Bolt Carrier Assembly and Charging Handle
Assembly into the Upper Receiver until they click firmly into place.
The Ejection Port Assembly should pop open.
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5. How To Change Your Barrel On Your AR-15
Install a barrel or Swap a old barrel for a new barrel.
This web teach you how to properly install a barrel and/or re-barrel
your AR-15 upper. This whole process, should take less than an hour.
If you can tighten a single nut, then you can change or install a
This section is going to start with how to remove a barrel from an
AR-15, and then how to re install another barrel. If you are installing
a barrel on a receiver that doesn’t already have a barrel on it, just
skip all the prior steps and jump right into installing the barrel.
Required Tools:
You will need some more specialized tools to properly install a barrel
on your upper receiver. Here is what you will need to do it right:
1. A upper receiver action block. I went with the Bushmaster model
2. A armorer’s wrench. Based on what I read about all the choices, I
chose the DPMS model (~$35):
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3. A small punch to knock out the gas tube roll pin. I used a 1/16”
drill bit because I did not have a punch that small.
4. A set of snap ring pliers. I had a set laying around, but you can
get these at any hardware store.
5. Molybdenum-Disulfide grease (per the TM) This is for the upper
receiver threads. This is found at any auto parts store or hardware
store for cheap. If you JUST CANT seem to find it, buy this grease
from Bushmaster:
6. A vise. Pretty much any size will do, but must be firmly mounted
to a bench of some sort.
Installation Instructions:
1. First thing is first. Remove the upper from the rifle. Remove the
bolt/carrier/charging handle from the upper.
2. Remove the hand-guards from the upper. (This assumes you
have typical carbine/rifle guards) You do this by pulling on the delta
ring toward the receiver, while using your other hand to slip off the
upper and lower guard. It’s a little tricky at first, but you will get the
hang of it with practice.
3. Next, we need to knock out the roll pin that holds the gas tube
into the front sight assembly. The correct size if 5/64". Try finding
a 5/64" punch at your local hardware store!. Use a 1/16” punch. I
didn't have one that small, so I just used a really small drill bit to
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knock it out. Tt can be tapped out from either direction. Here is a
close-up of the roll pin to knock out:
4. Once that is knocked out, you can remove the gas tube. Pull the
tube from the front sight base into the upper receiver, until the
tube can clear the front sight, then pull it forward to remove it.
Sometimes they can be stubborn, and you might have to LIGHTLY
grab the tube with a pair of pliers and tap the plier’s rearward with a
light hammer. Don’t crush the gas tube. If for any reason you
damage it, they are cheap. Replace with a new one. Note the gas
port on the tube faces down, and note the hole for the roll pin:
5. Now, we are ready to slap on the action block. It only goes on one
way, so you cannot screw it up. Clamp the upper/block into the vise
as shown:
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6. Take your armorer’s wrench out, push it onto the barrel nut, and
unscrew the nut. There is spring pressure here, so you must push in
towards the receiver whille you turn. It uses standard threads.
Righty-tighty, Lefty-loosey. Once it breaks free, it should unscrew
fairly easily. Take off the delta ring assembly as shown:
7. Now, your barrel will just pull straight from the receiver. Remove
the barrel.
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8. At this point, we need to remove the delta ring, spring, and
snap-ring that holds it all together. Grab your snap ring pliers, and
slide off the snap ring, spring, and delta ring as shown:
9. Halfway there! Now, we need to clean the surfaces of the new
barrel, and the threaded area of the upper receiver, to make sure
they are free of grit and particles that might keep them from going
together smoothly. I like to use gunscrubber, or brake parts cleaner
for this. Then apply a little moly grease to the threads of the upper
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10. If necessary, assemble the delta ring assembly on the new
barrel. Now, slide the new barrel into the receiver. There is a locator
stub on the barrel that fits in a notch in the upper receiver. If there is
any play here, line up your front sight so that it is the straightest with
the rear sights. Sometimes, it *may* be necessary to file this notch
open in one direction, if your front sight will not line up straight. I
don’t recommend cutting anything at first; assemble your barrel, and
only perform this procedure if your sights require a lot of windage
adjustment in one direction to zero it.
11. Thread on the barrel nut. Be careful not to cross-thread it, so just
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go easy at first. Some people like to take a short piece of gas tube or
3/16" bar and insert into the receiver, to hold the spring/snap ring
from spinning as you tighten the barrel nut. Then use your armorers
tool to get the barrel nut snug (not fully tight). Inspect the barrel nut
lugs, and continue to tighten the nut until the lugs line up with the
gas tube hole in the receiver. Once that is done, you need to make
sure that the hole in the spring and the snap ring is aligned so you
can insert the gas tube. Insert the gas tube through the barrel nut,
delta ring, and into the receiver. Then insert the other end into the
front sight block:
12. Now, you can remove the upper from the vise. Tap the roll pin
back into the front sight block to hold the gas tube in place. Install
the handguards.
13. Sight the upper in and go shooting!
Common Barrel Installation Questions & Answers
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Can I use a barrel vise instead of an action block?
Yes, but a barrel vise will often allow the barrel to spin while
torquing, which will mar the barrel. The barrel vise will also put all
the pressure during barreling on the index pin in the upper receiver.
This will increase the potential for a canted front sight. It is not as
simple or effective as an action block. Spend the $38.
What about the torquing three times, to 80ft/lbs like the
manual says?
While using a torque wrench is never a bad idea, it is not required.
Snug it up, three times, then line up with next gas tube hole.
Sometimes this will take a lot of force, sometimes just a little. If you
aren’t sure, or nervous, go to the local auto parts store and borrow a
torque wrench for ft. pounds. The point of snugging it up three
times, is to mate the aluminum upper receiver threads together with
the barrel nut.
What about checking the headspace after I assemble?
While checking your headspace is never a bad idea, it isn't required
for this operation. The headspace of an AR is set by the bolt's fit into
the barrel extension. As long as you are using a good quality bolt and
barrel, that was headspaced by the manufacturer, you are good to
go. If you are assembling very old/used barrel/bolt, then you might
want to consider checking headspace. Changing the barrel has no
effect on headspace, because the barrel's seating in the upper
receiver makes no difference, it is all in the bolt and barrel extension.
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I am confused about the moly-grease for the upper receiver
threads. I can’t seem to find any grease that just says "moly
grease" on it?
A4. There is a lot of noise about this in the AR-15 Community. Truth
is, you just want a decent grease that will keep the barrel nut from
galling, and has a high temperature rating so it wont run out and
dissipate over time. It's really not all that important. Any standard
wheel bearing grease, available at ANY auto parts store, will do just
fine. If you are extremely anal, just buy this grease from
"I installed my barrel, but my FSB seems canted in one
direction, and in order to zero, I had to move my rear sight
all the way to one side, and sometimes it still wont zero
because I ran out of windage."
This is a very common problem with a very easy fix. It's caused by
small differences between the upper receiver notch and barrel pin.
And here's how you fix it:
Unscrew the barrel nut. With the barrel in the upper receiver, check
the sight alignment by eyeballing it. If it's canted to one side, try and
twist the barrel in the upper. If it won't move far enough, then take a
jeweler's file and very carefully file the side of the upper receiver
notch to open it up until the front sight can sit up straight.
Before reinstalling the barrel nut, you have to tighten up the receiver
notch so the barrel won't move around while you're cranking down
on the nut. With the barrel in the receiver, take a small hammer and
punch and very lightly peen down the loose side of the notch.
Careful, tap lightly because it doesn't take much. What you'll see is a
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slight flattening of the threads right next to the barrel pin. That's it!
6. Install your own free-float Fore-End
Many shooters are not satisfied with the standard AR-15 forearm and
therefore want to change it to a more functional and definitely better
looking free float forearm system.
This section will walk you through the process of installing one of the
more common Free Float rail systems on the market. There are a
wide variety of free float systems on the market and each one has its
own unique installation method. However despite their differences,
they all follow the same basic methods, so by using this guide in
conjunction with your tubes instructions you will have no trouble
installing your own free float system.
The tube we will be installing is a YHM brand ultralight carbine float
tube which can be had for around $90.
Required Tools:
Since this procedure requires removal of the barrel/barrel nut, you
will need many of the same tools you used to build your upper
receiver. You will need a action block, armorers wrench, 1/16" punch,
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snap ring pliers, moly-grease, and a vise.
In addition, depending on the free float tube you choose, you might
need a special float tube wrench.
You will also need a couple of punches. You just need a good sized
(1/4") soft brass punch and a steel 1/8" punch.
Installation Instructions:
1. Remove the upper from the rifle. Remove the hand guards. Using
the instructions listed in the above posts; remove the barrel from the
upper receiver. (You don’t have to fully remove the barrel.... just the
barrel nut/delta ring assembly, and you could leave the gas tube in
the FSB) We will be assuming a full disassembly is required for this
guide) you MUST remove any type of muzzle device first.... flash
hiders, muzzle brake, etc... If these are permanently mounted, then
they will have to be removed. Depending on their method of
attachment, it may be advisable to have a competent gunsmith
remove them and reinstall them.
Now we need to remove the FSB (front sight base) from the barrel.
The pins in the FSB are typically tapered. This means they can only
be removed one way. Look on both sides of the FSB and determine
which side of the pins is the SMALLER end. It should be the left side,
and we will be knocking the pins out from left to right. This is not
always the case, so always inspect your front sight base carefully.
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2. Support the barrel so that when we knock the pins out, we won’t
stress the barrel at all... I used a couple pieces of 2x4. Using a large
diameter (~1/4") brass punch, firmly knock the pins loose. Use
masking tape all round the FSB is you are worried you might slip and
scratch something. I must admit... on most of the barrels I have
done, a couple sharp hits with a punch knocked the pins loose.... but
I finally had one Bushmaster 20" barrel that the pins absolutely
would not come loose on. I ended up having to Dremel the FSB down
and then was able to punch them out, but I ruined the FSB. I was
replacing with a flip up FSB anyway, so it wasn’t a great concern...
but keep this in mind, should you come across one that is not very
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It will take the most force just to break the pins loose... once they
are loose, we can use the small punch to tap them all the way out:
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3. Now, lubricate the FSB and the area on the barrel in front of the
FSB with CLP, WD40, gun oil...etc... this it to ensure we will scratch
the barrel as little as possible upon removing the FSB. Wiggle the FSB
back and forth to loosen it... you may need to put the barrel back in
the upper receiver to hold it for this step. Then, pull the FSB from the
barrel, going slow and taking care. If you go slowly, you shouldnt
place any marks on the barrel from this step. Remove the barrel nut
and delta ring as well:
4. Disassemble the YHM free float... into the float tube, aluminum
barrel nut, and float tube lock nut.
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5. Insert the barrel into the upper receiver. Apply a little moly grease
to the threads of the upper receiver.
6. Install the barrel nut, and get it snug (this should be tightened just
like any other barrel nut, torque it to spec).... then tighten until you
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align with the next possible gas tube hole. Slip the gas tube in from
the rear to ensure you are aligned:
7. Install the float tube lock nut. Thread it all the way to the rear,
flush with the back edge of the barrel nut. I like to use a little blue
Locktite on this, to ensure it won’t back off in the field. A little Loctite
makes all the difference!
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8. Spin on the float tube.... right up to the lock nut. Ensure the rail is
aligned with the rail on the upper receiver. I used a A3 carry handle,
half on the receiver, and half on the float rail, to achieve this. Then
tighten the locking nut. You can use the YHM tool for this, or a
hammer/punch/flat blade screwdriver.
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9. Now install the FSB back on the barrel, and the gas tube.
Remember to put the roll pin back in the gas tube if you removed it:
10. Using the large brass punch, tap the taper pins back in, from the
RIGHT, to the LEFT, this time. driving them home.
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11. DONE! Wasn’t that simple? Finished product... time to go
Common Free Float Tube Questions & Answers
How do you replace the front sight post and make it plumb,
so it's not to far left or right?
If you are removing and reinstalling the same FSB on the same
barrel, you cannot screw it up. The taper holes are drilled in the
barrel, and in the FSB.... and when taking it off/reinstalling it on the
same barrel, it will line up perfectly where it was before. There is no
room for "play". The taper pins as you drive them in will line it back
up exactly where it was drilled.
Can a second person hold the upper during tightening to
save the cost of a bench vice, bench, and $40 action block?
NO. The torque involved is too great for that.... you could rig up
some type of fixture, but if the upper is not properly supported, risk
of damage is high.
What about headspace after removing/installing the barrel?
If all you are doing is installing the FF tube on an assembled rifle,
using the same bolt/barrel as before, then there is absolutely no
reason to concern yourself with headspace, because it is not affected
by changing such things.
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AR-15 Rifle Diagrams
Upper Receiver & Barrel Diagram
(1) Handguard Assembly
(2) Gas Tube Pin
(3) Gas Tube
(4) Flash Suppressor/Compensator
(5) Peel Washer
(6) Handguard Slip Ring Retaining Ring
(7) Handguard Slip Ring Spring
(8) Handguard Slip Ring
(9) Upper Receiver Assembly
(10) Barrel Assembly
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Upper Receiver & Rear Sight Assembly
(1) Rear Sight Assembly
(2) Rear Sight Windage Knob Retaining Pin
(3) Rear Sight Windage Knob
(4) Rear Sight Windage Knob Helical Spring
(5) Rear Sight Windage Knob Ball Bearing
(6) Rear Sight Windage Screw
(7) Rear Sight Aperture
(8) Rear Sight Flat Spring
(9) Rear Sight Base
(10) Rear Sight Retaining Pin
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(11) Rear Sight Elevation Helical Spring
(12) Rear Sight Elevation Index Ball Bearing
(13) Rear Sight Elevation Index Helical Spring
(14) Rear Sight Elevation Index Screw
(15) Rear Sight Elevation Index
(16) Rear Sight Elevation Knob
(17) Ejection Port Cover Retaining Ring
(18) Ejection Port Cover Pin
(19) Ejection Port Cover Helical Spring
(20) Ejection Port Cover
(21) Forward Assist Retaining Pin
(22) Forward Assist Assembly
(23) Forward Assist Helical Compression Spring
(24) Upper Receiver
Forward Assist Assembly
1) Forward Assist Pawl Retaining Pin
(2) Forward Assist Pawl
(3) Forward Assist Pawl Detent
(4) Forward Assist Pawl Helical Compression Spring
(5) Forward Assist Plunger
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Barrel Assembly
(1) Front Sight Post
(2) Front Sight Post Detent
(3) Front Sight Post Detent Helical Spring
(4) Front Sight Pins
(5) Sling Swivel Tubular Rivet
(6) Sling Swivel
Charging Handle Assembly
(1) Charging Handle Latch Pin
(2) Charging Handle Latch
(3) Charging Handle Latch Helical Spring
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(4) Charging Handle
Lower Receiver and Buttstock Assembly
(1) Grip Machine Screw
(2) Grip Lock Washer
(3) Grip
(4) Safety Detent Helical Spring
(5) Safety Detent
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(6) Lower Receiver Extension Self Locking Screw
(7) Buttstock Assembly
(8) Stepped Spacer
(9) Takedown Pin Detent Helical Spring
(10) Takedown Pin Detent
(11) Takedown Pin
(12) Pivot Pin
(13) Buffer Assembly
(14) Recoil Spring
(15) Bolt Catch Pin
(16) Bolt Catch
(17) Bolt Catch Plunger
(18) Bolt Catch Helical Compression Spring
(19) Magazine Catch
(20) Magazine Catch Button
(21) Magazine Catch Helical Spring
(22) Automatic Sear Pin
(23) Sear
(24) Selector Lever
(25) Hammer And Trigger Spring
(26) Hammer Assembly
(27) Disconnector
(28) Disconnector
(29) Trigger Assembly
(30) Lower Receiver and Receiver Extension Assembly
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Lower Receiver Assembly
(1) Trigger Guard Pin
(2) Trigger Guard
(3) Lower Receiver Extension
(4) Buffer Retainer
(5) Buffer Retainer Helical Spring
(6) Lower Receiver
Hammer Assembly
(1) Hammer Helical Spring
(2) Burst Cam Helical Spring
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(3) Burst Cam
(4) Hammer and Hammer Pin Retainer Assembly
Trigger Assembly
(1) Trigger Helical Torsion Spring
(2) Disconnector Helical Spring
(3) Trigger
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Complete Rifle
(1) Magazine
(2) Small Arms Sling
(3) Bolt Carrier Assembly
(4) Charging Handle Assembly
(5) Upper Receiver and Barrel Assembly
(6) Lower Receiver and Buttstock Assembly
6. Properly Sight In Your New AR-15 Rifle
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The AR-15 rifle has two adjustable sights- front and rear. Zeroing
elevation adjustments are made using the front sight, and windage
adjustments with the rear.
The rear sight has an elevation knob with range indicators from 300
to 800 meters and two apertures for range. One aperture is marked
0-2 for short range from 0-200 meters and the unmarked aperture
for normal range from 300 to 800 meters. This unmarked aperture is
used in conjunction with the elevation knob for 300-800 meter
The rear sight also consists of a windage knob on the right side of
the sight. Each click of the windage knob will move the strike of the
round from 1/8 inch at 25 meters to 4 inches at 800 meters. A
windage knob pointer is on the windage knob.
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The front sight consists of a rotating sight post with a spring loaded
detent. This detent can be depressed using a sight adjustment tool,
or using a sharp point such as a cartridge tip.
Establish Zero
The following procedure will establish a zero at 25 meters, and your
AR-15 will be set with a 300 meter battle sight zero. This means that
all shots will be within a 9" circle at all ranges up to 300 meters.
Establish Mechanical Zero •
Align the windage indicator mark on the 0-2 aperture with the
center line of the windage scale (the unmarked aperture is up)
Rotate the elevation knob down until the range scale 8/3 (300meter) mark is aligned with the mark on the left side of the
Rotate the front sight post up or down as required until the
base of the front sight post is flush with the top of the sight
post well.
Carefully aim and fire each shot of a 3-shot group at a paper target
set up at 25 meters. If your shots are not striking the point-of-aim,
then adjust your sights.
To raise the next shot group, rotate the front sight post in the
direction marked UP (clockwise)
To lower the next shot group, rotate the front sight post in the
direction marked DOWN (counter-clockwise)
To move the next shot group left, turn windage knob
To move the next shot group right, turn the windage knob
Continue to fire 3-shot groups and adjust the sights until you have a
tight group at the point of aim.
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Once this is done, the unmarked aperture is automatically zeroed.
Rifle is now combat-zeroed all other ranges on the elevation knob are
also zeroed, so to engage target at say 500 meters, turn wheel to 5.
Now Get Out There and Shoot that Black Rifle!
8. Where To Buy Parts For Your Rifle
AR-15 Parts and Accessories Retailers
Over the last several years there has been a huge amount of growth
in the AR-15 industry. New companies are springing out of the
woodwork offering every imaginable type of part or accessory for AR15’s. It would be utterly ridiculous for me to try and give you a
comprehensive list of suppliers with as many as are out there. So
instead, I am going to share with you my favorite AR-15 related on
and offline retailers. Through these companies listed below you will
easily be able to create whatever style AR-15 you want.
Stag Arms:
Rock River Arms:
Larue Tactical:
Midwest Industries:
PK Firearms:
Bravo Company:
Global Tactical:
Comand Arms:
Rainier Arms:
AIM Surplus:
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