Introducing the Dirty Bird Industries Multi-Cal Forged Ambidextrous (MCF-A) Lower Receiver. When evaluating a lower, first priority is making sure the basics are done right.

Start with Quality Forgings

All MCF-A lowers are machined from top-tier 7075 Aluminum Forgings from Cerro Fabricated Products. It is a common misconception that all forgings are created equal. Cerro Fabricated Products has been a leader in precision forging, machining, heat treating and more since 1915.

Meticulous Machining

We wanted perfection, so we teamed up with the folks at MVB Industries. MVB, best known for their innovative ARC-X PDW Stock, is one of the industries’ best kept secrets. And while we’d love to keep them all for ourselves, we can’t talk about the quality of this lower without giving huge props to their team. Lots of companies are known for their creative vision, others are known for their unwavering attention to detail. MVB does both, and they do it very, very well.

A Quality-Control Centered Process

You’ll notice that in addition to ATF issued serial numbers, all of the lowers feature a unique identifier machined near the pistol grip interface. This is for tracking each individual unit throughout the production process. This added step allows QC staff to trace any potential quality issues back to an exact machine and a given batch, no matter how long it has been since that unit was produced.

Practical Improvements

It is one thing to add features to a battle proven design that is over 60 years old. There are some pretty crazy lowers out there, but are they practical? Do they sacrifice reliability? Do they make the lower more difficult to service or upgrade?

Ambidextrous Bolt Catch / Release

The Dirty Bird MCF-A Lower Receiver uses MVB’s patent pending mechanism that implements an Ambidextrous Bolt Catch / Release with elegance, rather than complexity.

• The mechanism both releases and actuates the bolt catch automatically. If the bolt is already in battery, hitting the lever will raise the bolt catch, enabling you to lock the bolt back. If the bolt is locked-back, hitting the lever will release the bolt. Simple.
• The mechanism is non-interfering, meaning that if the Ambi bolt lever is damaged during hard-use or movement is blocked by debris, the standard bolt catch / release paddle still functions flawlessly.
• The mechanism consists of only 4 proprietary components, all of which are machined from Billet S7 Tool Steel and QPQ Nitrided which means pretty much anything on the lower would break before they do.
• Utilizes zero hex screws. Instead, the Ambi Bolt Catch lever is installed with a standard bolt-catch roll pin. This simplifies things and gives the unit a higher level of serviceability.

Self-Adjusting Receiver Tensioner

The MCF-A utilizes a spring-loaded plunger to reduce slop between the upper and lower receiver. No more tension screws or accu-wedges.

Made in the USA

Backed by the Dirty Bird Limited Lifetime Warranty

*Black color is type 3 hard anodized per mil-spec. Other colors will be Cerakote.

*Limited compatibility with anti-walk / anti-rotation pins. We can confirm compatibility with Dirty Bird Brand Anti-Walk pins.

*Not compatible with third party bolt catches.

Take a look at our other AR-15 Lower Receivers here!