The 5.56mm Hybrid M4 carbine built with C3 Defense lower,…

The 5.56mm Hybrid M4 carbine built with C3 Defense lower, DPMS upper receiver and Choate stock.

One of the most interesting and gratifying phenomenons I have seen during the recent uptick in firearms ownership is the rise of the workbench custom AR. The Stoner-based rifle platform is infinitely modifiable and upgrades or additions are relatively simple to install.

Naturally, every firearm is made of “parts” or components that are carefully assembled in the factory. Certain items require meticulous manufacturing. The barrel comes instantly to mind followed by the upper and lower receivers. For this project I wanted to assemble my very own custom M4 using parts from a number of reputable manufacturers.

Lower Receiver: C3 Defense
AR style rifles are composed of myriad parts, but the component that is actually classified as a “firearm” is the lower receiver. The lower receiver, minus springs, trigger, stock, etc. is the serialized component and the one part that must be transferred through a registered FFL holder.

For this project I would secure a stripped lower receiver from C3 Defense. At first glance it was obvious that this part was well made. The lower receiver is machined from a solid billet for strength, giving the receiver a symmetrical, squared shape.

C3 has included some special features on their lowers. For instance, there is a tension adjustment screw at the base just below the buffer tube. This allows the end user to reduce/eliminate the “play” normally found between the upper and lower receiver. The magazine well is flared to ease loading and they have textured the front grip where many shooters like to hold the rifle.

C3 Defense solid billet lower receiver.

This particular receiver is standard black but they also make them in OD Green, Natural Earth (tan) and Dark Earth (coyote). C3 markets receiver sets with matching uppers and lowers both stripped and the same color. If you’d rather just purchase the entire gun they have complete rifles as well.

Upper Receiver: DPMS
For the upper receiver I would use a completed receiver assembly from DPMS. This particular unit was their AP4 assembly. The unit included a 16-inch barrel with NATO spec flash suppressor. A genuine 5.56x45mm chamber was used and the rifling is 1-in-9-inch right-hand twist.

Barrel material is 4140 chrome-moly steel. The receiver is a flattop design with an A3 carrying handle. A forged “A-frame” front sight housing can be adjusted for elevation and a fully adjustable A2 rear sight allows for windage and long distance elevation.

In place of the Panther Arms GlacierGuards that were shipped with the upper assembly I ordered a six-rail solid aluminum forend also from DPMS. This would allow me to install the accessories I desired up front.

The upper assembly included all the internal parts; bolt and bolt carrier, charging handle, forward assist, barrel nut, gas tube, etc. It arrived ready to mate with a lower. Speaking of the lower, as I mentioned it was a “stripped” model. No trigger, springs, pins, or other parts.

DPMS sells complete lower receiver kits for the AR rifle. The package includes everything you need to assemble an AR lower receiver, including the trigger, hammer, disconnector, safety and all the springs, the pivot and take down pins,

bolt catch and pistol grip. Aside from the A2 pistol grip all these items would go into the gun.

Stock: Choate
One of the last big pieces of the puzzle was the stock, buffer, and buffer tube. Several years ago I tested out a new telescoping buttstock from Choate Machine & Tool. I was impressed by the rock solid, rhino-tough construction and when I was putting this piece together I decided to have another look.

Since my initial introduction, Choate has made a few improvements to the stock. They trimmed it a bit to shave off some weight but it is still rock solid. Battery storage compartments are found on both sides of it. The stock has five-separate telescoping positions and a deep-checkered rubber buttplate.

As I required all the stock parts I ordered Choate’s stock/buffer/spring kit. If you already have a tube and simply want to switch stocks you can purchase that piece separately. The tube is aluminum and the stock is high-impact polymer. While I was at it, I ordered a single-point sling adapter from Choate as well.

CSAT rear aperture made by XS Sights.

Load Comments
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