CPS MEDIUM AR PLATFORM STOCK

B5 Systems CPS Medium Stock – Precision-Driven, Adjustable Comfort

The B5 Systems Collapsible Precision Stock (CPS) – Medium is our go-to stock for AR-15 precision platforms at Ally Munitions. It’s the exact stock we use on our in-house test rifles for ammo development and performance validation. Why? Because the CPS Medium hits the perfect balance between comfort, repeatability, and field-ready durability.

Designed for shooters who demand more than basic functionality, this stock provides excellent adjustability, a longer cheekpiece for better weld versatility, and a flat bottom ideal for use with rear bags in precision shooting environments.

We only stock the Medium version—not only because it’s our preferred model, but because the longer cheekpiece makes it more versatile for real-world applications.

Key Features

• Cheekpiece: Extended 4 3/8" length for improved and consistent cheek weld

• Adjustability: Tool-less adjustable cheek height and length of pull (LOP)

• Bottom Profile: Flat bottom ideal for rear bag support in precision setups

• Material: Molded from high-strength polymer, reinforced for field durability

• QD Mounts: Dual ambidextrous QD sling swivel sockets

• Hardware: Manganese-phosphate finished steel hardware

• Buttpad: Overmolded rubber pad for comfort and anti-slip grip

Dimensions:

• Weight: 20.65 oz (585g)

• Overall Length (collapsed): 8.7”

• Length of Pull: 11.2”–14.6”

• Cheekpiece Length: 4 3/8"

• Cheekpiece Width: 2”

• Fits: Mil-Spec buffer tubes

Color Options Available:
Black, Flat Dark Earth (FDE), OD Green, Wolf Grey, Coyote Brown

Made in the USA

Why We Recommend It

We believe the CPS Medium is one of the best stocks available for precision-focused AR-15 builds. When choosing accuracy potential over overall weight, this stock provides all the real, usable features a precision shooter needs:

• Unmatched Adjustability – Quick and secure changes to cheek height and LOP

• Comfort-Driven Design – Longer cheek riser and ergonomic shape support long-range sessions

• Precision-Ready Geometry – Flat bottom makes it perfect for rear bag use or supported shooting positions

This is our top recommendation when tuning a rifle for accuracy, comfort, and practical adjustability.

Pro Build Tips

• After adjusting cheek height, verify that bolt carrier group movement is not impeded—especially with extended charging handles.

• Apply a light coat of grease to the adjustment rods to maintain smooth function over time.

• When zeroing your optic, lock in your cheek height setting for repeatable weld and better shot-to-shot consistency.

Ally Munitions Insider Note

We’ll be releasing a video and color-matching master list soon that breaks down which pistol grip manufacturers best match each B5 stock color—perfect for builders chasing visual cohesion and function