The Phase 5 Weapon Systems Carbine Mini Stock Assembly (brand part no. CMSA) combines Phase 5’s Universal Mini Stock (UMS) with a HexOne buffer tube for a compact, fixed-stock solution on AR-15 and AR-10 builds. Phase 5 precision machines both pieces in-house from USA-sourced raw billet aluminum, cutting the HexOne buffer tube from 7075-T7 and the UMS from 6061-T6. The hexagonal buffer tube design is noticeably thicker and more rugged than a standard mil-spec receiver extension, and the UMS’s smaller footprint and bottom curve anchor the stock against the chest for faster, easier position changes.

Key Specifications

• Combines the Universal Mini Stock (UMS) with the HexOne buffer tube in one kit.
• Fits both the AR-15 and AR-10 platforms.
• HexOne buffer tube machined from 7075-T7 aluminum.
• UMS machined from 6061-T6 aluminum.
• Hexagonal design is noticeably thicker and more rugged than a mil-spec receiver extension.
• Rated for 5.56 NATO, .300 BLK, 7.62×39, and .308, plus PCC calibers with a different buffer/spring.
• UMS’s smaller footprint and bottom curve anchor the stock against the chest for faster position changes.
• Also compatible with most mil-spec carbine receiver extensions and round tubes.
• Finished in black, precision machined in the USA.

Frequently Asked Questions

What platforms does this kit fit? AR-15 and AR-10.

What calibers is it rated for? 5.56 NATO, .300 BLK, 7.62×39, and .308, and PCC calibers like 9mm, .40 S&W, and .45 ACP with a different buffer and spring.

Is the UMS compatible with other buffer tubes? Yes, it also works with most mil-spec carbine receiver extensions and round tubes.

Buy the Phase 5 Weapon Systems Carbine Mini Stock Assembly

Get a compact, rugged fixed-stock setup built from American billet aluminum. Order it from our AR buffer system selection at our Lubbock, Texas gun shop for fast, direct shipping.