The B5 Systems Modular Platform Stock (brand part no. MPS-1555) in Coyote Brown pairs a folding steel hinge with a fully adjustable, mil-spec-compatible carbine stock body for shooters who want a compact, durable platform on a Picatinny-equipped rifle. Built from durable composite materials with steel hardware, it’s designed for hard use on a duty carbine, home-defense rifle, or a folding-stock AR build where overall length matters. A spring-assist cheekpiece and dual sling-mount options round out a stock that’s meant to work as hard as the rifle it rides on. It mounts directly to any standard 1913 Picatinny interface for a fast, tool-friendly install.

Key Specifications

• Features an integral left-side folding steel hinge for a shorter overall footprint when the rifle isn’t in use.
• Offers adjustable length of pull so the stock can be tuned to the shooter and their gear.
• Includes a spring-assist cheekpiece that returns to position automatically after folding.
• Provides ambidextrous fixed sling mounts for traditional two-point or single-point setups.
• Adds ambidextrous limited-rotation QD sling mounts for quick-detach sling attachment on either side.
• Uses a nonslip buttpad to keep the stock planted against the shoulder under recoil.
• Attaches via a standard 1913 Picatinny mount for straightforward installation.
• Built from durable composite materials with steel hardware for long-term reliability.
• Overall stock length measures 8.06 inches.

Frequently Asked Questions

Does the hinge fold to the left or right? The integral hinge folds to the left side of the rifle.

Can I adjust length of pull after folding? Yes, length of pull adjusts independently of the folding hinge, so fit doesn’t change when you fold or deploy the stock.

What mount does it use? It attaches to any standard 1913 Picatinny rail interface rather than a receiver extension tube.

Buy the B5 Systems Modular Platform Stock

A folding Picatinny stock built for shooters who need to shave inches off their rifle without giving up adjustability or a stable cheek weld. Order the Coyote Brown B5 Systems Modular Platform Stock from our Lubbock, Texas gun shop for fast, direct shipping, and browse more rifle stocks to finish your build.