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Magpul ACS Carbine Storage Stock - Commercial Spec AR-15 - MAG371

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Shipping cost is $5.50 for orders under $35. We ship with UPS and USPS. 

Most orders ship out within 24 hours

You will receive tracking information immediately at the time of shipment. To expedite shipping, we may ship your order from multiple warehouses.  

We have a 90-day no-hassle return policy. We pay return shipping.

If you need to request a return, contact us at and we will send you a return label

After 90 days, defective items will still be covered under the manufacturer’s warranty, where applicable.

Please refer to the product listing for warranty details. If you have specific warranty questions, contact us at We may direct you to pursue your warranty claim directly with the manufacturer.

Your satisfaction is our #1 priority

If you're dissatisfied with your purchase, in any way, please contact us at - we will do our best to make it right.

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The patented Magpul ACS (Adaptable Carbine/Storage) – Commercial-Spec Model is a drop-in replacement buttstock for AR15/M16 carbines using commercial-spec sized receiver extension tubes. A streamlined, anti-snag profile shields the release latch to prevent accidental activation. Similar to the Magpul CTR®, the ACS also features a supplemental friction lock system that minimizes excessive stock movement for enhanced weapon stability and accuracy*. Dual, rear accessible, water-resistant battery storage tubes and an integral storage compartment in the butt of the stock provides multiple storage options. The ACS comes standard with a 0.30" thick rubber butt-pad which provides positive shoulder purchase to prevent slippage even with body armor or modular gear.

Made in U.S.A.


Mounts on commercial-spec sized carbine receiver extension tube (not included) from manufacturers such as Bushmaster, DPMS, Olympic, and others (please see the note below)

Sloping cheek weld provides a wide contact surface for user comfort

Two water-resistant battery storage tubes located on the left and right sides of the stock

Each tube will store up to three CR123 lithium or two AA batteries

Tubes are accessible from the rear via a tethered, hand-removable rubber plug

Storage compartment in tail of stock with positive latching access door on right hand side

Supplemental friction lock minimizes accuracy robbing wobble*

Shielded release latch prevents snagging and accidental operation

Premium chrome-silicon lock spring provides positive locking and long service life

Replaceable 0.30" Rubber Butt-Pad offers an anti-slip surface and increases impact protection

Compatible with Magpul ASAP® and other receiver-mount sling attachments

Sling Mounts

Mid - Now includes the QD Swivel Sling Mount that fits up to 1.5" push-button swivels

Rear/Bottom - 1.00" sling loop

Optional Accessories**

Extended Rubber Butt-Pad, 0.55"

Enhanced Rubber Butt-Pad, 0.70"


ACS, Commercial-Spec (stock configuration)

Weight: 0.88 lb.

Weight, w/ Rec. Extension: 1.22 lb.

Length, Maximum: 7.95 in.

Width, Maximum: 2.58 in.

LOP Adjustment Range: 3.80 in.

LOP, M4 Collapsed: 11.75 in.

LOP, M4 Extended: 15.55 in.

NOTE: There are two basic sizes of M4 Carbine receiver extensions (buffer tubes): mil-spec and commercial-spec. If you have a mil-spec extension on your rifle, make sure to order the Mil-Spec ACS. Please see the "Related Info" section above to determine which tube you have.

* Friction lock performance may vary depending on the host receiver extension's dimensional tolerances.

** Specifications based on extended-length (slant-back) commercial-spec receiver extension and may vary depending on tube manufacturer.

Standard Rubber Butt-Pad, 0.30" weight: 0.08 lb. Optional Extended Rubber Butt-Pad, 0.55" (weight: 0.11 lb.) or Enhanced Butt-Pad, 0.70" (weight: 0.13 lb.) may be used with either Mil-Spec or Commercial-Spec ACS stocks.

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