Assemble an AR15 upper

(Note: you can click on a picture for a link to Brownells for the major part or tool in that picture so you can purchase)

(Note2: the pictures here are of my AR 15 6.5 Grendel upper, assembly uses the same tools and the same process as a standard 5.56 or .223 AR15)

First things first, to get going on your build you will want to make sure you have the right tools for the job.

Upper vice block

Barrel Wrench



punch tools


Assembling the AR15 Upper:

I will be posting the steps of assembling a stripped upper receiver when I have the money together to buy one and the parts.


Put the Ar15 Barrel onto the upper:

Start by putting the upper receiver into the Upper Vice Block

Put the Vice Block in the Vice, the purpose behind this is to allow enough grip to allow for tightening the barrel nut without crushing the upper, or mangling it…

Grease the Threads on the Upper

Now you take the barrel and line up the peg with the notch on the upper, this notch makes sure the feed rams are lined up properly, and the gas port is on top.

With this build I am using a Yankee Hill free float foregrip, so we replace the GI barrel nut/delta ring and such with the barrel nut that came with the free float, and we carefully put it over the barrel.  And here we are threading it on.  One additional thing to notice is that this Yankee Hill free float tube, the diamond series, has an additional ring on the barrel nut, this will be used latter to tighten against the Tube when it is properly in place.

You now tighten up the barrel nut, you will be using a special tool for the AR15, a barrel nut wrench.  You can see the square cut out in the wrench, this is so you can use a torque wrench to tighten the barrel nut to between 35 and 50 pounds, the upper limit is 80 pounds.  In reality this poundage is not CRITICAL, it is a good idea and recommended, however you are limited to were you stop the nut at since the gas tube will be passing through it via one of the many holes or notches.  Basically you will tighten it up three times, on the third time you will align one of the holes/notches so the gas tube can run through it properly.  The exactness of this alignment can affect the placement of the top rail of a rail system, in this case since we are using the diamond series quad rail it was very important, you could really see it if it was off a little because of the picatinny rail spanning to the upper.  The barrel wrench has three pins, each will go in a notch or hole for the gas tube on the barrel nut.

Once the barrel nut is secured, since we are using a free float tube in this build, we will now thread on the Yankee Hill Machine Diamond Free Float Quad Rail.  Be careful not to scratch the barrel or the rail system as you pass it along the barrel to thread it, use both hands and slide your fingers along the barrel to prevent the Rail system from touching it.  Also be sure to line up the rail of the Upper with the top rail of the Quad Rail System, take extra care that it is right.

It is now time for the gas tube and gas block.  First off get the gas tube roll pin, you want to get it started into one side of the gas block.  The gas tube roll pin is hollow so this will still allow for you to line up the right hole in the gas tube before pushing the pin in all the way.  while lining up the gas tube, make sure the intake port of the tube is pointing the right direction, this would be towards the barrel.  The way I do this process is I use two blocks of wood partially carved to match the gas block, then I hold the gas block steady with the vice.  Make sure the gas tube roll pin holes are facing up and down so that you can use a hammer and punch tool to push the pin in.  After each tap of the hammer make sure the gas tube is lined up properly.  This picture shows what a gas tube pinned to the gas block.

Now you will be blocking up the upper again in the vice and sliding on the gas block, again be very careful not to mark the barrel as you carefully slide on the gas block.  This specific gas block is held on with two set screws from the bottom by using an allen wrench.  You will be sliding the gas tube through the hole in the barrel nut and the upper receiver.  Be very careful that you do not bend the gas tube, if it gets bent the gas key on the bolt carrier will hit the tube and cause damage to your rifle.  With a gas block like this that uses screws it is always a good idea to use some light loc tight to secure the screws and prevent them from coming out.  Be sure that before you put the gas block on you mark with a pencil where the gas port is on the barrel, and also make a mark on the gas block where the port is, this makes it easier to align the gas ports.

Once you have lined up the gas ports on the barrel and the gas block, it is time to secure the gas block with the set screws – I recommend you use the loc tight.  If you are not sure you have aligned the gas ports, wait to use the loc tight until after you have verified that your rifle cycles rounds properly.  If the ports are not lined up then there will not be the pressure that pushes the carrier back to eject the spent cartridges and load a new round.  Use the allen wrench to tighten the screws, you want them tightened for two reasons, one is to keep the gas block from twisting and the second is to prevent gas leaking.

more to come!