The patented Magpul ACS (Adaptable Carbine/Storage) – Mil-Spec Model is a drop-in replacement buttstock for AR15/M16 carbines using mil-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.

Features
Mounts on mil-spec sized carbine receiver extension tube (not included) from manufacturers such as Colt, Armalite, S&W, LMT, 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"
Specifications**
ACS, Mil-Spec (stock configuration)
Weight: 0.88 lb.
Weight, w/ Rec. Extension: 1.14 lb.
Length, Maximum: 7.95 in.
Width, Maximum: 2.58 in.
LOP Adjustment Range: 3.25 in.
LOP, M4 Collapsed: 11.75 in.
LOP, M4 Extended: 15.00 in.
NOTE: There are two basic sizes of M4 Carbine receiver extensions (buffer tubes): mil-spec and commercial-spec. If you have a commercial-spec extension on your rifle, make sure to order the Commercial-Spec ACS.

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

** Specifications based on standard-length (flat-back) M4 Carbine 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.