Tools We Didn't Categorize (Miscellaneous)
There are lots of miscellaneous tools that we recommend for the serious armorer.
R: Required
r: Recommended
O: Optional
Needle Nose Pliers (r)
Needle nose pliers come in handy when you need to grab and hold small parts (e.g. the C-clip for the dust cover).
10-32 Thumb Screw (r)
We recommend a 3/4″ 10-32 knurled thumb screw when installing the gas block. with a properly dimpled barrel, this tool allows you to properly index and hold the gas block in place while you install the first gas block set screw.
Gas Block Alignment Tool (r*)
The gas block needs to be properly aligned with the gas port on the barrel. Failure to align properly will result in inefficient or insufficient gas flow.
We recommend using a borescope and gas system illuminator. However, if you do not have or want to buy/build these, there is a less expensive option.
The Gas Block Genie is a simple plastic device that clamps onto the gas block journal of the barrel. By aligning the device with the gas port, you can mark the barrel and gas block such that you are able to align them properly, without directly witnessing the alignment.
Borescope (r*)
The gas block needs to be properly aligned with the gas port on the barrel. Failure to align properly will result in inefficient or insufficient gas flow.
We recommend using a borescope and gas system illuminator. This allows you to visually verify the alignment of the gas block, taking all of the guesswork out of the job.
We recommend the Teslong NTG200H borescope. The bore rod folds for easy storage. There is a focal length adjustment segment on the bore rod that allows quick focus adjustment. The monitor is packed with features, including brightness adjustment and image capture. The set comes with several side view mirrors for any bore diameter.
Gas System Illuminator (r*)
In order to properly visualize the alignment of the gas block and gas port using a borescope, you need to illuminate the gas system.
There used to be a company called Xtreme Effects that made a product called the Gas Block Illuminator. It was essentially a fiber optic cable and a fiber optic illuminator on a dimmer switch. The company no longer exists, so we have created a copy using parts that can be purchased on Amazon.com for less than $15.
We will be posting assembly instructions soon.
1/8" Drill Rod (r)
We use two 12″ lengths of 1/8″ drill rod to help time the muzzle device appropriately. We feed one rod through the muzzle device (or rest it on a horizontal flat) and rest the other in a slot in the picatinny rail of the upper. When viewed from the muzzle, you can easily see if the rods (and therefore, the muzzle device) are aligned.
You can also accomplish this with bamboo skewers.
Pivot Pin Installation Tool (r)
Installing the pivot pin (and detent/spring) without a tools is a pain in the rear. We have lost many detents trying to do this over the years, and have nearly lost an eye a few times.
Luckily, there are tools that make this process VERY easy.
Our preferred tool for installing the pivot pin is from Obsidian Arms. Along with a 1/16″ pin punch for installation, this tool is simple and efficient. Obsidian Arms offers both an AR-15 and AR-10 version. Note that if you buy the Obsidian Arms Roll Pin set, the AR-15 version is included.
A similar option to the Obsidian Arms tool would be a clevis pin. You need a 1/4″ clevis pin for the AR-15. The pivot pin for the AR-10 is 0.270″, and you probably won’t find a clevis pin of this diameter.
Real Avid makes a tool of a similar design to the function of the Obsidian Arms pin, but it is not compatible with all AR-10/LR308 lowers, so we don’t recommend it.
For the AR-15, the most idiot proof tool is made by Real Avid. They make a plastic version and a professional version made of metal. Both do the same job and really make this job easy enough that anyone can do it.
AR-15:
AR-10:
Magazine Button Installation Tool (r)
When installing the magazine release button, you need to depress the button into the lower receiver to thread the magazine catch into it.
We use the Mercy Firearms MBAG, though this has apparently been discontinued. If you have access to a 3D printer, these “enhanced magazine button” prints can accomplish the same function.
You can also use a nylon punch or other non-marring object to depress the magazine release button.
3/32" Drill Bit (r)
A long time ago, we encountered an issue seating the pivot detent spring fully into the lower receiver. It turned out to be residual polishing media stuck in the cavity. Since then, we systematically clear the cavity with a 3/32″ drill bit on every lower that we assemble. We find polishing media in a significant portion of lowers, so this is a very simple and inexpensive practice that should be standard.
Trigger Pin Tool (r)
Aligning the trigger and hammer with the lower receiver holes takes some finesse.
Some triggers (e.g. HIPERFIRE) come with a tapered drift pin that makes alignment easy and makes installation of the hammer pin much easier. While not strictly necessary, it is a useful tool. It is worth noting that the Obsidian Arms roll pin punch set that we recommend comes with one of these.
We also find that some lower receivers (especially those with a Cerakote finish) have tight trigger/hammer pin holes. We use another tool for “boring” out the holes, which helps with pin installation (especially oversized pins like the Geissele pins). The Geissele Trigger Fitting Pin is the ideal tool for the job.
Barrel Dimpling Jig (r*)
If your barrel is not dimpled, we strongly recommend buying a barrel dimpling jig. This tool allows you to precisely drill a depression in the barrel opposite the gas port to give added assurance to the alignment and security of of the gas block. Without a dimpled barrel, the gas block may rotate on the barrel, leading to reduced efficiency or blockage of the gas system.
The best tool for the job is the SLR Rifleworks Barrel Dimpling Jig (note that this does NOT come with the required drill bit). One of the distinguishing features of this tool is the replaceable drill bushings. KAK Industry also makes a good product, and it comes with all of the necessary tools.
Barrel Nut Alignment Tool (r*)
If you are installing a barrel nut that requires the gas tube to pass through it (the Aero Precision Enhanced uppers do not have this issue), you need to be VERY careful with aligning the barrel nut, upper receiver, and gas block. Failure to do so will cause the gas tube to contact the upper/barrel nut (if it passes through), and this can have 2 effects:
- It can push the tip of the gas tube out of alignment with the gas key on the BCG, causing the gas key to strike and damage the gas tube.
- It can cause the gas tube to rub the barrel nut/upper receiver, which can erode the contact point of the gas tube and cause premature failure of the gas tube.
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You can use a 4″ section of 1/8″ drill rod and a bolt carrier to verify alignment from within the upper receiver.
You can also purchase a dedicated tool. Â
Gas Key Staking Jig (O*)
If you are building a bolt carrier group from individual components, or if you need to replace the gas key for any reason, you will need a gas key staking jig. This tool displaces material from the gas key against the gas key screws to lock them in place.
The best gas key staking tools are manufactured by Michiguns. The MOACKS and MOACKS II are the gold standard. Note that the MOACKS II seems to have been discontinued.
Brownells makes a similar tool, however the design of the staking bolts is not ideal (too sharp).
Headspace Gauges (O)
Headspace is an important issue in the AR platform. Read our Sister Cartridges Deep Dive articles for a comprehensive explanation and assessment.
We use Forster headspace gauges for most of our needs. The following specifications may be useful:
| Chamber | GO | NO GO | FIELD |
| .223 Rem | 1.4636″ | 1.4666″ | 1.4696″ |
| 5.56 NATO | 1.4646″ | 1.4706″ | 1.4736″ |
| .308 Win | 1.6300″ | 1.6340″ | 1.6380″ |
| 7.62 NATO | 1.6355″ | Â — | 1.6455″ |
Trigger Pull Gauge (O)
This tool is probably only “needed” by the most OCD armorers and competition shooters.
If you have an adjustable pull drop in trigger, you may want to tune your trigger pull to a precise value for one reason or another.
Or you may want to verify manufacturer specifications/claims.
In general, we recommend focusing on the way a trigger pull feels, rather than quantifying it. But if you want more objective data, this tool can help.
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