Magpul ACS Stock: Adjustability and Storage for All the Field Needs

One of the longest running variants of polymer stocks from Magpul Industries, the ACS Stock is a multi-use, multi-function stock for AR-patterned rifles. The ACS provides for improved cheek weld, storage, and can be adjusted for varying lengths-of-pull to meet the needs of any end-user.

The ACS (Adaptable Carbine/Storage) Stock was developed in 2009 to be among the many in Magpul’s line of drop-in replacement, polymer buttstocks. It combines the storage of the STR stock, with some of the more traditional features of the CTR. It is available in a variety of receiver extension tube compatibility (featuring in Mil-Spec). The ACS has an overall length of 8” and a width of 2.5” at its widest point.

Dual water-resistant battery storage compartments, with rear-facing rubberized plugs, are sufficient enough to allow for the storage of two CR123A lithium batteries, or two AA batteries. In turn, these parallel battery storage compartments give the ACS a broader area for an angled cheek piece which translates to a greater cheek weld with the shooter. Additionally, dual integral storage compartments in the rear of the stock allow for multiple storage options for odd-shaped items.

The reinforced and compact A-frame design of the ACS includes a shielded operation lever that “unlocks” the stock from the buffer tube. The corresponding friction locking system then allows the ACS to move to any position of the buffer tube, and once a position is determined, to maintain a positive position with minimal movement.

A reversible QD mounting cup, a 0.30” thick replaceable rubberized buttstock, and an integral sling loop (to accommodate a sling up to 1” wide) finish off the additional features to the ACS.


  • Length of Pull (LOP) Collapsed…11.6 in.
  • LOP Extended ……………………14.9 in.
  • LOP Adjustment Range………….3.3 in.

The ACS Stock is available in Black (featured), FDE, Urban Grey, and OD Green. It is also available for Mil-Spec (featured) and Commercial receiver extension tubes.  

Product Evaluation Scores:

  • Cost – Average (3/5): At $89.95 the ACS stock represents an ideal balance of materials over cost wherein the efficient design allows for essential storage and user function, at a modest price over the more basic CTR ($59.95) stock and advanced STR ($79.95). Magpul has made its products synonymous with aftermarket rifle accessories and the ACS has a lot to offer shooters from the basic to more advanced. In comparison VLTOR’s EMOD ($114.95) is perhaps the closest comparator in both material and function, followed closely by B5 System’s SOPMOD ($58.99). Given that the ACS’s price falls roughly between these market alternatives, and is more at the upper end of Magpul’s product line, that gives it an appropriate (or average) score rating within the overall market.
  • Comfort – Good (4/5): The most significant aspect of the ACS’s comfort was its improved dimensions for a larger cheek weld over more traditional A2-type stocks. The tube itself was angled with a wider base that gave it a quasi-triangular appearance. This design not only gave the shooter more real-estate for contact when shouldering, but sufficient space for the two storage compartments that run the length of the stock and under it. The clip enclosure on the door of the storage compartment was a little difficult to function, but that was actually more ideal so as not to inadvertently open during field use. The two rubberized plugs had a comfortable fit inside the storage tubes, and were easily removed with the fingertip. Internet research illustrated that some variances in buffer tube dimensions may result in a minor amount of wiggle between the ACS and buffer tube, but there are a number of personalized and simple remedies to resolve that issue.
  • Durability – Excellent (5/5): The ACS was made from the same polymer material as Magpul’s magazines and other stocks, this gave it a good degree of resiliency and durability throughout evaluation. The thickness of the stock’s tube and A-frame help ensured any force or tension was transferred throughout the design and mitigated. In addition to several drop tests, the ACS was used for several stressor iterations going from prone to standing while using the ACS as a means to brace the movement. In all cases the ACS supported the pressure and was never compromised beyond some minor surface marring.
  • Functionality – Good (4/5): Functionally the ACS’s operational and friction lock both provided a solid connection to the buffer tube and the stock, keeping the overall ACS in place. Movement along the various positions was solid and the operational lock avoided any accidental slippage. As noted, the biggest aspect of the ACS was the improved cheek weld over the CTR or other A2 style buttstocks with added storage capacity. While there was a little added bulk due to the angled sides of the tube and its storage compartments, its added bulk was minimal at most. The ability of the QD cup to be moved from either side was accomplished simply by unscrewing the hardware and reassembling on the opposite side. The only noted negative from a functional aspect was the removable plugs for the storage tubes did not have any type of attached lanyard or connection, making them very susceptible to loss when removed, and something Magpul may want to consider in future designs.
  • Weight – Fair (2/5): Weighing in at 14.1 ounces, the ACS is in the mid-range of the Magpul family of rifle stocks with the lighter CTR weighing 8.8 ounces, and the UBR being 23.36 ounces. But for its advantages; improved cheek weld, storage and adjustability, the ACS is one of the more logical options for those looking for an appropriate blend of lightweight function and form. In comparison however, the VLTOR’s EMOD (14 ounces) and the B5 System’s SOPMOD (10.25 ounces) both come in at or just under the weight of the ACS making it one of the heavier options. But the weight of the ACS did aid in absorbing some of the recoil, but it is still a fair weight amid other alternatives.

Overall Rating – Above Average (18/25)

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I am reviewing this product as a courtesy to the manufacturer and via STL Shooting Enthusiasts, so that I can evaluate it and provide my honest feedback. I am not bound by any written, verbal, or implied contract to give positive reviews. All views are my own, and based off my personal experience with the product.

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