Magpul ACS Carbine Stock Mil-Spec for AR-15/M4
Mix and match across the range: 2 items save 5%, 3 save 10%, 4 or more save 15% on your whole basket.
Fits AR-15/M4 rifles with a Mil-Spec-diameter carbine receiver extension (buffer tube). Check your tube specification before ordering.
Not sure it fits your rifle? Ask us before you order
The Magpul ACS is a mil-spec carbine stock with dual onboard storage compartments for AR-15 and M4 rifles, fitting any Mil-Spec-diameter receiver extension.
The self-contained carbine stock — the ACS locks down like a fixed stock and carries like a supply cache.
The Magpul ACS Carbine Stock (MAG370) — Adaptable Carbine/Storage — pairs a friction-lock system that clamps the stock rigid against the receiver extension with dual water-resistant storage compartments in the cheek housing. The result is a collapsible stock with fixed-stock stability that also keeps batteries, spare parts and small mission essentials sealed inside the rifle itself.
The wide, contoured cheek weld surface supports precise work behind optics, the rubber buttpad plants in the shoulder, and sling integration covers loops and QD alike. For duty rifles and go-bag carbines that must be self-sufficient, the ACS remains the most complete stock Magpul builds at this weight.
Fits AR-15/M4 rifles running a Mil-Spec-diameter carbine receiver extension (buffer tube). A commercial-spec tube is a different diameter and will not take this stock, so confirm your tube specification before ordering. Slide on, set length of pull, engage the friction lock — then load the compartments and forget them until needed.
| Platform | AR-15 / M4 |
|---|---|
| Fits | Mil-Spec carbine receiver extension |
| Type | Collapsible carbine stock with dual storage compartments |
| Finish | Black, Flat Dark Earth, Olive Drab Green |
| Adjustment | Friction lock |
| Brand | Magpul Industries |
| MPN | MAG370-BLK · MAG370-FDE · MAG370-ODG |
Stability, storage, sorted. Order the ACS today — imported from the USA with all duties paid by us and dispatched tracked from the UK in 7–10 business days, with nothing to pay on delivery.
Explore more: Rifle & Shotgun Stocks, Precision Rifle Stocks, AR-15 Parts or browse all Magpul.
| Platform | AR-15 / M4 |
|---|---|
| Fits | Mil-Spec carbine receiver extension |
| Type | Collapsible carbine stock with dual storage compartments |
| Finish | Black, Flat Dark Earth, Olive Drab Green |
| Adjustment | Friction lock |
| Brand | Magpul Industries |
| MPN | MAG370-BLK · MAG370-FDE · MAG370-ODG |
| Category | Rifle Stock |
| Shipping weight | 1.0 kg |
| Barcode | 873750001005 |
£5 tracked UK delivery on every order via Royal Mail Tracked 24. Our products are ordered in from the manufacturer rather than held in UK stock, so please allow 7 to 10 business days (Monday to Friday, excluding bank holidays) from the date of your order for it to reach you. Tracking details are emailed on dispatch. UK delivery only.
You have 30 days from receiving your order to cancel it for any reason, then 14 days to send it back unused and in its original packaging. Faulty, damaged or incorrect items are replaced or refunded and we cover reasonable return postage. Refunds go back to your original payment method within 14 days of receiving the return.
It fits AR-15/M4 rifles running a Mil-Spec-diameter carbine receiver extension. A commercial-spec tube is a different diameter and will not take this stock, so confirm your tube specification before ordering. Measuring the tube is the quickest way to be certain.
The MAG370 has two separate compartments in the stock body, so you can keep spares and small kit divided rather than loose in one cavity. It is the fuller-bodied option in the ACS family. If you would rather have a slimmer stock with simple battery tubes, the <a href="/products/magpul-acs-l-carbine-ar-15-stock-mil-spec-mag378">ACS-L (MAG378)</a> is the lighter sibling.
The friction lock takes the play out of the stock on the buffer tube, so the stock sits tighter and feels less rattly against the cheek. It works alongside the normal adjustment lever rather than replacing it. You still collapse and extend the stock the usual way.
Black, Flat Dark Earth and Olive Drab Green are all offered. Provided your buffer tube is Mil-Spec, no extra hardware is required to fit it. Other stocks worth comparing are in <a href="/collections/magpul-ar-15-stocks">Magpul AR-15 stocks</a>.
This stock is sent from the United Kingdom with £5 tracked UK delivery in 7–10 business days and you'll get tracking by email when it ships. If it turns out not to match your receiver extension, see our returns policy or <a href="/pages/contact">contact us</a> and we'll help sort it.
7 to 10 business days from the date of your order. Every order is sent Royal Mail Tracked for a flat £5 and you receive tracking details by email when it is dispatched.
Yes. We list only genuine parts and optics from the brands shown, ordered in from the manufacturer for your order.
Compatibility notes on this page come from the manufacturer. If you are unsure, email us with your make and model before ordering and we will check rather than guess.
Yes. Bundle & Save applies automatically in your basket: 5% off when you buy 2 items, 10% off at 3 items and 15% off at 4 or more. It works across the whole range, so you can mix and match, and there is no code to enter.
Yes — you have 30 days from delivery to cancel for any reason, as long as the item is unused and in its original packaging. See our returns policy for the details.
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