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ACS® COLLAPSIBLE MIL-SPEC CARBINE STOCK FOR AR-15 Reviews & Ratings

The Magpul ACS (Adaptable Carbine/Storage) - Mil-Spec model is a drop-in replacement buttstock for AR15/M4 carbines using Mil-Spec sized receiver extension tubes. Dual, rear accessible, water-resistant battery storage tubes and an integral storage compartment in the butt of the stock provides multiple storage options.

Similar to the Magpul CTR®, the ACS also features an anti-snag release latch to prevent accidental activation along with a supplemental friction lock system that minimizes excessive stock movement for enhanced weapon stability and accuracy*. 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, LMT, S&W, and others (please see the note below)
Storage compartment in tail of stock with positive latching access door on right hand side
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 and tubes are accessible from the rear via a tethered, hand-removable rubber plug
Sloping cheek weld provides a wide contact surface for user comfort
Supplemental friction lock minimizes accuracy-robbing wobble*. Shielded release latch prevents snagging and accidental operation
Rubber butt-pad offers an anti-slip surface and increases impact protection
Premium chrome-silicon lock spring provides positive locking and long service life
Compatible with Magpul ASAP®, ASAP® QD, and other receiver-mount sling attachments
Mid - Included reversible Sling Mount Kit - TYPE 3 fits up to 1.5" push-button swivels (swivel not included) / Rear/Bottom - 1.00" sling loop
Made in the USA

SPECS

Collection: Collapsible Storage AR Stocks
Platform: AR10, AR15, M4, M16, M110, SR25
Compatibility; Mil-Spec sized carbine receiver extension tube (not included) from manufacturers such as Colt, Armalite, LMT, S&W, and others
LOP, M4 Collapsed: ~11.6 in.
LOP, M4 Extended; ~14.9 in.
LOP Adjustment Range: 3.3 in.
Length, max: 8.0 in.
Weight: 14.1 oz.
Weight, w/ receiver extension: 18.1 oz.
Width, max: 2.5 in.
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.

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 you will need to swap it over to a Mil-Spec size tube to utilize this stock.

See all of our AR15s and AR15 parts here.

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Reviews Summary

The ACS® Collapsible Mil-Spec Carbine Stock for AR-15 impresses users with its solid construction, excellent cheek weld, and practical storage features, making it a popular choice among seasoned builders and shooters. However, some reviewers noted installation difficulties and issues with sling attachment clearance. Overall, it's considered a reliable and durable stock option.

What Reviewers Are Saying

Product Quality

85%

Most reviewers praise the excellent build quality of the ACS stock, highlighting its solid construction and durability. Many users appreciate the well-engineered design, which contributes to a reliable shooting experience and enhances overall performance.

Cheek Weld and Comfort

75%

The cheek weld provided by the ACS stock is frequently lauded as a standout feature. Reviewers report that it allows for improved sight alignment and a comfortable shooting position, making a significant difference during use.

Storage Features

65%

The storage compartments integrated into the stock are seen as a valuable asset, allowing users to keep essential items like batteries and spare parts readily accessible. The added utility of these compartments enhances the stock's functionality.

Installation Difficulty

45%

Several users encountered challenges during installation, particularly with the stock's locking mechanism that requires a tool for proper fitting. While some found it manageable, others wished for a more straightforward installation process.

Value for Money

70%

Reviewers consistently remark on the competitive pricing of the ACS stock compared to similar products. Many feel it offers great value given its quality and features, often choosing it over more expensive alternatives.

Sling Attachment Design

30%

A few reviews noted issues with the position of the quick-detach sling stud, which can cause interference with slings and affect functionality. Suggestions for improvement were made, but this did not greatly detract from overall satisfaction with the product.

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Good part and good vendors

This is a very nice stock. Unfortunately, I managed to break the first one. I called Brownells and they shipped a new one out to me right away. They didn't ask me if I did something stupid or if it was my fault. They shipped a new one with no questions asked. In my defense, the instructions on the Magpull site are not written very well. Read the instructions twice before installing and you will be happy with this product.

Would you recommend this? Yes, I would recommend to a friend

by Terry on April 02, 2026

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Company

This item is perfect for A5 buffer tube 7 position . Magpul products are well made with good material. Great engineers who designs them. And not let us forget about Brownells company!! What a great place to shop

Would you recommend this? Yes, I would recommend to a friend

by Lino Raquipiso on October 31, 2024

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Great stock a bit on the heavy side

Very nice stock, very well made, heavily built so I think it should be very durable. It has a lot of storage space for batteries or other small bits.

by Dan Smith on March 23, 2024

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Magpul ACS stock from Brownells

Typical Magpul quality and Brownells great pricing.

by Ron Braunhardt on December 15, 2023

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Best AR Stock

I've always felt the Magpul ACS Stock was the best AR stock available. Offering a solid platform with comfort and durability.

by JOHN WESLEY on November 26, 2023

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Only stocks I use.

All of my ARs and Springfield M1A s.o.c.o.m have this but stock. I also run limb savor pads on this stock. Sticks to body armor relly well.

Easy on, easy off

Got one of these included with a rifle. Now I put them on everything. Not sure why everyone is having issues putting them on. Just pull down on the two metal cylinders sticking out the side of the lock and slide it on. It's not easy, but if my arthritic old hands attached to my 150lb body can do it, what's your excuse? Ladies excepted of course.

Great Stock!

I've used Magpul MOE & CTR stocks before and they always worked great. I decided to try the ACS on my most current build and I absolutely love it! It takes a bit more effort to put it on, but it's still very simple. It is rock solid when locked in place and the cheekwelds are awesome. You can definitely feel the improvement in quality when you shoulder your rifle. Honestly, I don't know if I'll use the storage compartments much as I don't like things rattling around, but this is just a fantastic stock for the money. I will absolutely buy this again.

Great stock!

I own three ACS and one ACS-L stocks, nuff said.

Storage

The double lock/latch eliminates that annoying wobble. There is absolutely no wobble. I cant find a stock that offers more storage. You can even store a firing pin in one of the two battery compartments. Do I even need to mention cheek weld.... yes its amazing as youd guess. The side storage compartment is perfect for backup parts or tactical treats.