Stop Fighting Your Parts. Start Building Your Rifle.

You know the drill. You get an 80% lower, the parts kit, and then the real “fun” begins: chasing a spring across the garage, cursing at a detent pin that won’t seat, and marring your fresh finish with makeshift tools. We’ve been there. That’s why we didn’t just sell you another raw billet blank. We engineered the hassles out.

This Premium Fire/Safe Marked Billet 80% Lower is a direct result of listening to builders in our shop. The two most frustrating points in any AR-15 lower build are now solved with simple, clean engineering: threaded bolt catch release pin hole and a threaded rear takedown detent hole. No more drift pins, no more hammering, no more launching parts into the void. You use the included screws and hex key for a precise, secure, and utterly frustration-free install. It’s a small change that makes the entire process smoother and more professional.

What You’re Getting: A Complete Foundation

This isn’t just a lower. It’s a complete lower assembly kit to get you from 80% to a fully functional receiver ready for your upper. Here’s exactly what’s in the box:

• One (1) Billet 80% Lower Receiver: Machined from solid 7075-T6 aluminum billet, anodized in Mil-Spec black. It features clean, deep FIRE and SAFE engravings and a broached magwell for flawless magazine fit.
• One (1) Lower Parts Kit (LPK): All the internal fire control group parts, pins, springs, and detents you need to complete the lower.
• One (1) Butt Stock: A standard MIL-Spec compatible stock for a solid cheek weld.
• One (1) Buffer Tube Assembly: Includes buffer tube, buffer, buffer spring, and castle nut.
• Install Screws & Hex Key: For the threaded bolt catch and rear takedown detent holes.

You supply the tools for the final machining step (we recommend a quality jig and router), the dedication, and the final vision. We supply a rock-solid, American-made foundation that works with you, not against you.

Why 7075-T6 Billet Matters

You’ll see a lot of lowers out there. Forged receivers are tough and proven, but billet is a step above in precision and strength for the home builder. We start with a solid block of 7075-T6 aluminum—the same alloy used in aircraft frames—and CNC machine it to exacting tolerances. This process allows for cleaner lines, sharper edges, and a more rigid final product compared to forging. There’s zero porosity, zero inconsistency. It’s a denser, more durable starting point. When you pick this lower up, you feel the heft and see the machine marks. This is a serious component for a serious build.

Built Here, For You. No Paperwork.

Every single one of these lower blanks is 100% made in the USA in our facility. We control the machining, the anodizing, and the quality check. More importantly, because this is an unfinished receiver (80%), it is NOT a firearm under federal law. No FFL transfer is required. It ships directly to your door. The completion of the fire control cavity is your responsibility, in accordance with all local and federal laws. Know your laws before you buy and build.

Who This Is For

This kit is for the builder who understands that a rifle is only as good as its foundation. It’s for the person who takes pride in the craft, who wants the satisfaction of a custom-built firearm without the typical headaches of assembly. It’s for those who value the simplicity of threaded install points and the uncompromising strength of billet aluminum. If you’re doing one build to learn, or your tenth build for a specific purpose, this lower assembly removes the common obstacles so you can focus on the precision of your mill work and the quality of the final product.

You’re not just buying a part. You’re buying a better building experience and a superior result. Grab the Premium Billet 80% Lower Assembly from Polymer80Market.com and build it right the first time.