OSA Premium Lower Parts Kit (LPK)
The OSA Premium Lower Parts Kit is built for shooters who refuse to settle for standard mil-spec components. Every major control has been upgraded using premium parts from Forward Controls Design, with a Geissele G2S Two-Stage Trigger completing one of the finest lower parts kits available.
Designed for duty rifles, defensive carbines, and premium custom builds, this kit combines exceptional ergonomics, outstanding machining, and proven reliability into one package.
Includes
- Forward Controls PF-040 Takedown & Pivot Pins
- Takedown & Pivot Detents
- Takedown & Pivot Springs
- Forward Controls ABC (Augmented Bolt Catch) – Center Bias (Dimpled or Serrated)
- Bolt Catch Plunger
- Bolt Catch Spring
- Bolt Catch Roll Pin
- Forward Controls Low Profile Magazine Catch
- Forward Controls EMR-H Magazine Release (Dimpled or Serrated)
- Magazine Catch Spring
- Forward Controls ASF 50° Ambidextrous Safety Selector
- Selector Detent
- Selector Spring
- Forward Controls TGW Winter Trigger Guard
- Forward Controls CNF Castle Nut
- Forward Controls ESF-H1 End Plate
- Forward Controls RBF Buffer Retainer
- Buffer Retainer Spring
- Geissele G2S Two-Stage Trigger
- All remaining detents and springs
Features
- Premium components from Forward Controls Design
- Geissele G2S Two-Stage Trigger included
- 50° Ambidextrous Safety Selector
- Enhanced bolt catch and magazine controls
- Premium castle nut and end plate
- Winter trigger guard
- Precision-machined steel components
- Made in the USA
- Compatible with standard AR-15 lower receivers
Our Thoughts
The lower receiver is where you'll interact with your rifle every single time you pick it up.
That's why we believe it's worth investing in quality controls.
The OSA Premium LPK replaces virtually every standard mil-spec control with thoughtfully engineered upgrades from Forward Controls Design—a company widely regarded for producing some of the finest AR components in the industry.
The ABC (Augmented Bolt Catch) offers a larger, more ergonomic surface for locking and releasing the bolt, while the EMR-H Magazine Release provides improved purchase without being oversized or prone to accidental activation.
The ASF 50° Ambidextrous Safety Selector is another standout feature. The shorter throw allows for faster manipulation while maintaining positive engagement and an excellent tactile feel.
At the heart of the kit is the Geissele G2S Two-Stage Trigger.
The G2S delivers the same clean, predictable trigger break that Geissele is known for at a more approachable price point. It provides a smooth first stage followed by a crisp second-stage break, making it equally at home on defensive carbines, precision rifles, and general-purpose builds.
To round out the package, we've included premium hardware like the CNF Castle Nut, ESF-H1 End Plate, and RBF Buffer Retainer, ensuring the quality extends beyond the controls you see every day.
Final Verdict
The OSA Premium Lower Parts Kit isn't just a collection of upgraded parts—it's the same combination of components we'd choose when building one of our own rifles.
With premium controls from Forward Controls Design, the proven Geissele G2S Trigger, and exceptional attention to detail throughout, this kit transforms a standard lower receiver into a rifle that feels noticeably more refined every time you run it.
If you're building an AR-15 where quality matters, the OSA Premium LPK is one upgrade you'll appreciate every time you manipulate the controls or press the trigger.
