Ar 15 lower

An AR-15 lower receiver is the foundation of every AR build — and, legally, it is the firearm. The lower houses the trigger group, magazine well, and stock, and it carries the serial number, which means it’s the one part of an AR-15 that must transfer through a licensed FFL dealer. Whether you’re starting a custom build or replacing a lower, this category covers stripped and complete lowers and what you need to know. Pair a lower with an upper and bolt carrier group to build a complete AR-15.

Tatted Tacticals stocks AR-15 lowers from leading makers — stripped lowers for custom builds and complete lowers with the fire control group installed, ready to pair with an upper.

Stripped vs. Complete Lowers

A stripped lower is just the bare serialized receiver, giving builders a blank canvas to install their own trigger, stock, and parts kit. A complete lower comes assembled with the fire control group, trigger, grip, and stock — ready to mate with an upper. Stripped lowers offer maximum customization and a lower entry cost; complete lowers save assembly time and ensure everything’s properly installed. Both are the serialized firearm and transfer the same way through an FFL.

The FFL Requirement

Because the lower receiver is legally the firearm, it must ship to a licensed FFL dealer — never directly to you — where you complete ATF Form 4473 and a background check before taking possession. This applies to both stripped and complete lowers. The persistent “stripped lower, no FFL” idea is a misconception: a bare serialized lower is still a firearm under federal law and requires the same transfer. Review our state restrictions, as some states regulate lowers and AR features, and federal rules are published by the ATF.

Building on a Lower

A standard AR-15 lower accepts a wide range of calibers built on the platform — the caliber is determined by the upper and barrel, not the lower — so one lower can host a 5.56, .300 Blackout, or other AR-15-compatible upper. Note that AR-15 and AR-10/.308 lowers are different and not cross-compatible. Always follow the four rules of firearms safety, with guidance from the NSSF.

AR-15 Lower — Frequently Asked Questions

Do you need an FFL for a stripped AR-15 lower?

Yes. A stripped lower receiver is legally the firearm under federal law, even without any other parts installed, so it must transfer through a licensed FFL dealer with a Form 4473 and background check. The common “stripped lower, no FFL” claim is false — the serialized lower always requires FFL transfer, whether stripped or complete. Only non-serialized parts like uppers and BCGs ship directly.

What calibers can you build on an AR-15 lower?

A standard AR-15 lower can host many calibers, since the caliber is set by the upper and barrel, not the lower — including 5.56/.223, .300 Blackout, .350 Legend, .224 Valkyrie, and more. One lower can run different caliber uppers with the matching bolt and magazines. Note that AR-10/.308-class cartridges require an AR-10 lower, not an AR-15 lower, as the two platforms differ in size.

What is the difference between a stripped and complete lower?

A stripped lower is the bare serialized receiver with no internal parts, ideal for custom builds where you install your own trigger, grip, and stock. A complete lower comes fully assembled with the fire control group and furniture, ready to pair with an upper. Both are the serialized firearm requiring FFL transfer; the choice is between customization and convenience.

Is an AR-15 lower the same as an M16 lower?

They’re similar but not identical. An M16 lower is machined to accept full-auto fire control parts, making it a machine gun part subject to strict regulation, while a semi-automatic AR-15 lower is configured for semi-auto only. Civilian AR-15 lowers are semi-automatic firearms. Installing full-auto parts in any lower is illegal without proper licensing. Stick to semi-auto AR-15 components for a lawful civilian build.

Can you buy an AR-15 lower online?

Yes, but it must ship to a licensed FFL dealer near you, not directly to your home, since the lower is the serialized firearm. You complete the transfer, including a Form 4473 and background check, at the FFL. State laws vary and some restrict lowers or AR features, so confirm your local requirements before ordering. The upper and other parts can ship directly.