Magpul Stock MOE Collapsible AR-15 Carbine Synthetic Mil-Spec Black – MAG400-BLK

The Magpul Stock MOE Collapsible AR-15 Carbine stock in synthetic black, part number MAG400-BLK, is the definition of a sensible upgrade. It fits mil-spec carbine buffer tubes, it weighs almost nothing, and it costs a fraction of what a premium stock does while solving the same problems. For a huge number of builds, this is the correct answer rather than the budget answer.

What the Magpul Stock MOE Collapsible Design Gets Right

The MOE line exists to deliver the essential features without the extras that drive cost up. That means a stock body that is rigid where it needs to be, a comfortable cheek surface, and an adjustment mechanism that works reliably thousands of times. Nothing is included that you would not use.

This is for the builder finishing an AR-15 carbine on a budget that still has standards, the shooter replacing a rattly factory stock, and anyone setting up a rifle that multiple people will shoot. A collapsible stock lets a rifle fit a range of body sizes and clothing layers, which is exactly what a shared home defense or training rifle needs.

Key Features of This Stock

• Collapsible design with multiple length of pull positions, adapting the rifle to different shooters, gear, and shooting positions.
• Synthetic construction that resists impact, weather, and solvents without adding meaningful weight to the rear of the rifle.
• Mil-spec carbine buffer tube compatibility, matching the overwhelming majority of AR-15 builds in circulation.
• Black finish that matches standard AR furniture and hardware without any color matching guesswork.
• Magpul’s MOE styling with a comfortable cheek surface and clean lines that will not snag on gear.

Specifications and What They Mean

Mil-spec compatibility is the specification to verify before anything else. Mil-spec and commercial buffer tubes differ by a small amount in outside diameter, and a Magpul Stock MOE Collapsible unit built for mil-spec will not fit a commercial tube properly. Measure or check your build documentation if you are not certain which one you have.

The synthetic polymer construction is a genuine advantage over aluminum. Polymer flexes and absorbs impacts instead of denting, it does not get painfully cold in winter against a cheek, and it does not conduct heat. It is also completely unaffected by the solvents and lubricants that live in a cleaning kit.

Weight matters at the rear of a rifle more than most shooters realize. A lighter stock shifts balance forward, which most people find steadier for offhand shooting and faster for transitions between targets.

Installation, Use, and Care

Installation is tool free on a standard build. Depress the adjustment lever fully, slide the stock onto the buffer tube, and release the lever so it seats into a detent position. Cycle it through the full range and confirm it locks positively at every stop with no wobble. Check the buffer tube threading and the receiver end plate while you have the stock off, since those are the parts most likely to have loosened since the build.

Set your length of pull with the gear you will actually be wearing. A stock that fits perfectly in a shirt will feel long over a plate carrier or a heavy winter coat, which is precisely why a collapsible stock exists. Shorter positions for gear, longer positions for shirtsleeves and supported shooting.

Keep the buffer tube clean, since grit trapped between the tube and the stock accelerates wear and creates the rattle a good stock is supposed to prevent. Wipe both surfaces during normal cleaning and inspect the adjustment lever spring occasionally. The Magpul Stock MOE Collapsible carbine stock pairs well with the grips, handguards, and triggers stocked in our parts and upgrades category, so you can finish a build in one order.

Few parts from Magpul have earned their reputation as thoroughly as this one. Ships direct to your door, no FFL required.