What Is an 80 Percent Lower and Is It Legal
Woody's answers are based on published federal and state law. Not legal advice. Consult a licensed attorney for your specific situation.
An 80 percent lower is an unfinished firearm receiver that requires additional machining to become functional. Federal law generally considers them unregulated until completion, but state and local laws vary significantly.
What This Means for You
These unfinished receivers let you complete your own firearm legally in many jurisdictions without background checks or serial numbers. However, the regulatory landscape is shifting rapidly with new ATF interpretations and state-level restrictions affecting availability and legality.
The Detail
An 80 percent lower receiver is essentially a partially machined piece of aluminum, polymer, or steel that contains the basic shape and some features of a complete lower receiver but lacks the critical dimensions that would make it legally considered a firearm. The term "80 percent" is more marketing than precise measurement, since there's no official ATF specification for what percentage of completion triggers regulation. What matters legally is whether the fire control cavity is machined to the point where it could accept trigger components without additional work.
Federally, these unfinished receivers have traditionally been considered raw materials rather than firearms, meaning no background check, no serial number, and no transfer restrictions under normal circumstances. You can legally complete one for personal use in most states, provided you're not prohibited from owning firearms and you don't intend to sell it. The moment you finish machining the fire control pocket and safety selector hole to specification, you've manufactured a firearm under federal law.
The legal landscape around 80 percent lowers has become increasingly complex. The ATF has been reinterpreting what constitutes a firearm under federal law, particularly focusing on how readily a blank can be converted to a functional state. Some unfinished receivers that were previously unregulated are now being treated as firearms if they come with jigs, drill bits, or instructions that make completion straightforward.
State laws vary dramatically and change frequently. Some states like California, New York, and Connecticut have banned or heavily regulated unfinished receivers, while others maintain the federal standard. Many states that allow completion require you to serialize the finished firearm and some require registration. Local jurisdictions may have additional restrictions that override state law.
Build Impact
Before starting any 80 percent build, you need to research current federal, state, and local laws in your area since regulations change frequently and penalties can be severe. The completion process requires proper tooling and machining skills to ensure the finished receiver meets safety standards and legal dimensions.