Rifleshooter.com teams up with Brownell’s to update an old AR-15
The following article chronicles our build and is for informational purposes only.
Reflecting on the round count for the carbine I am currently shooting, I stop counting at 10,000 rounds. Consider this, the barrel was fairly heavily used when I purchased it a few years ago- now we are well past the point of getting my money’s worth out of it. The trigger pins had begun wearing away at the receiver until I installed KNS pins three years ago. Notably, most major AR15 manufacturers are represented in this rifle; the Colt upper and SOCOM profile barrel; Daniel Defense Omega Rail; Larue BUIS, Aimpoint mount and bolt carrier group; DPMS gas tube, buffer and ejection port cover; Magpul grip and MOE stock; Geiselle SSA trigger; Vltor butt stock extension, Bushmaster lower and VTAC sling. The hodge podge of parts are covered in multiples layers of chipped paint highlighted with various witness marks and arrows drawn on with an assortment of paint markers. This is a “Frankenrifle” in every sense.
Time to build a new rifle. Looking through my safe, I found my old Colt 6601, a pre 1994 20″ rifle with a 1/7 20″ government profile barrel. This rifle, equipped with A2 sights and an A2 stock is similar in appearance to the M16A2 I was first issued in the Marines. While there is a sentimental value to the configuration, I rarely shoot the rifle, and speaking to Marines currently in service, I was horrified to learn the 20″ guns are now referred to as “muskets”.
Before beginning the update, it is important to make the rifle safe and empty.
Begin by ensuring that the rifle is pointed in a safe direction, with the selector on “safe”. If a magazine were present, it would be removed. Then the bolt is locked to the rear and the chamber and magazine well are inspected TWICE to ensure that no ammunition is present.
Rifle is clear. Lets begin!
The bolt is released forward and the front and rear pivot pins removed. The upper and lower receiver are now separated.
Since the the entire upper receiver is going to be replaced, it will be stowed for later, sentimental use. The butt stock can now be disassembled.
The lower receiver is now stripped.
I started this upper receiver build by selecting the barrel I wanted to use. The choices in barrels may seem overwhelming at first, but the basics of selection are fairly easy. I prefer direct impingement guns to piston driven guns, so direct impingement it is. Barrel length, well that is easy, 16″. Sight radius is determined by the length of the gas system, rifle (longest) mid length or carbine (shortest). I selected the carbine gas system. Why? I have spare parts. Daniel Defense’s 16″ M4 profile barrel (100-005-853) fit the bill. Daniel Defense hammer forges, then chrome lines their barrels. This yields an incredibly durable product that last for thousands of rounds.
The barrel will be installed into a flat top upper receiver (100-005-853), that was included as part of a kit I received from Brownells. This kit includes a upper receiver, charging handle, hammer and complete bolt carrier group coated in Fail Zero’s proprietary EXO coating system which provides a permanent dry lubricity to the treated parts.
To address the small parts I will need to finish this build, I ordered a Colt upper receiver completion kit (080-000-607). The kit contains all of the small parts you need to turn your barrel assembly, hand guards, upper receiver, charging handle and bolt carrier group into a complete upper. The Colt kit costs slightly more then some of those by other vendors, but you get what you pay for. In this case, parts from the company who has been building this rifle for over 40 years.
I start by installing the forward assist into the upper receiver.
I like to start with the pin that retains the forward assist first. Use a roll pin holder to guide the pin and gently tap it in enough to start it. Be careful not to drive it in to the point where it will impede installation of the forward assist. I placed the upper on a rubber mat for this operation.
The spring slides over the forward assist’s body, then insert it into the upper. If you have an AR with a forward assist, you can reference the inside in order to properly align the forward assist pawl.
Push the forward assist in the remainder of the way and use a roll pin punch to drive the pin flush. The use of the proper punch is critical with roll pins, convention punches can damage the pins and slip off, possibly damaging the parts. The roll pin punch has a small guide in its center that prevents this from occurring.
Next step, install the ejection port cover. Here are the parts:
Begin by placing the “c” clip into the ejection port cover pin.
The remaining installation is simple. I start by inserting the ejection port cover pin into the ejection port cover. Once the pin is started, align the spring as shown below and finish pushing the pin through until the “c” clip hits the receiver. Close the cover and flip it open when you are done. The cover should be driven open by the spring, if the cover is not under tension to stay open, you installed the spring backwards.
Time to prep the barrel for installation. Begin by removing the front sight base. This can be a tricky process if your front sight base is installed with mil spec taper pins, this is the case with the Daniel Defense barrel. To aid in the process, Brownells makes an AR15 front sight bench block (080-000-252) specifically designed for the task. I have tried this with standard bench blocks and hockey pucks, this is another case where the right tool helps get the job done. Once the barrel is secured in the block, I start the pins with a short replaceable pin punch and then finish driving them out with a standard punch. Slide the front sight assembly off of the barrel and secure the pins. I typically keep a supply of small bags on hand to secure parts as I progress along.
This upper receiver will use a Daniel Defense FSP Rail Interface System II (RIS) in flat dark earth (100-005-809). Weighing in at 16.2 ounces, the RIS II rail system is constructed of aircraft grade aluminum and coated in military specification hard coat type III anodizing. It has 12.57″ of rail surface and a cut out to allow a standard front sight to protrude through the rail. Begin by placing the bolt up plate and the barrel nut onto the barrel.
Insert the barrel extension into the upper receiver. I typically put a light coat of oil on the barrel extension to help it slip into place. In this case I am using a light coat of Clenzoil Field and Range.
Now it’s time to torque the barrel onto the upper receiver. Begin by securing the upper in an upper receiver bench block. These blocks are typically equipped with a polymer insert to prevent receiver breakage.
Once the receiver is in a vise, use the Daniel Defense Lite Rail wrench to tighten the barrel nut. This wrench is not included. Do not use a single point steel spanner, you will end up gouging the aluminum barrel nut. Daniel Defense recommends between 50-75 foot pounds of torque be applied.
The barrel is now attached to the upper receiver. To proceed, we will need to attach the gas tube to the front sight base. This requires the carbine length gas tube and gas tube pin, both of which are included in the upper receiver completion kit.
With the gas tube attached to the front sight base assembly, the rail and front sight can be slid onto the barrel.
Once the four screws are installed, verify alignment of the rail and begin to tighten the six screws to between 29-32 inch pounds of torque. Daniel Defense recommends that you torque the center screws first, then the upper screws and finally the lower screws.
Now you can slide in the bottom part of the rail.
Installation of the rail is complete.
The Primary Weapons FSC 5.56 is an outstanding muzzle brake. Even though a 2.23 rifle doesn’t kick much, the reduction in muzzle flip is immediately noticeable.
I’ve installed these brakes in the past and indexing them can be tricky. Normally, alignment is accomplished through a crush washer or a peel washer. Primary Weapons now includes a “Muzzle Device Alignment Set”, this set includes three different thicknesses of washers, each offering a its own correction of the orientation of the muzzle.
Since the FSP RIS II rail is so long on this upper, the barrel cannot be secured in the vise using a barrel block. In this case we will use some rubber lined vise jaws.
Install the charging handle and the bolt carrier group and the upper receiver is complete. Time to work on the lower.
Since this lower receiver uses nonstandard .169″ trigger pins (most AR-15s use .154″ pins), trigger choice is somewhat restricted. Geiselle makes excellent triggers for the AR platform, and their service rifle trigger is available with .169″ trigger pins (100-003-615). The Geiselle Hi-Speed Service Trigger is an adjustable two stage trigger with a first stage from 3.2 to 5 pounds and a second stage from 1/2 to 1 1/2 pounds. More information on this trigger is available here, check out the trigger profile on the second page.
Since the trigger installation is quite complex, it will not be covered in detail here. If you would like complete instructions, Geiselle has a them posted on their website (installation instructions).
I used my trigger weight set (678-017-000) to verify the trigger could pick up a 4.5 pound weight (this is the lightest I like my triggers).
Note: Colt used to install hardened steel sear blocks in their lower receivers. These were not required by law, but installed by the company. If you plan on using this trigger in a lower with a sear block like I did, you will need to remove the sear block. The block was very difficult to remove and is designed to destroy the receiver. I Google’d “Colt sear block removal” and found a few links that offered advice. Basically you cut the block lengthwise with a Dremel and the side pins fall out. Then you pull up on the block itself.