What is the Legal Definition of Firearm, Receiver, Frame

When discussing or debating any topic, especially one as contentious as guns, it is essential that the people engaged in discussion use agreed upon terms. We can't properly convey all we want to say to someone who speaks an unfamiliar language. In this way, our discussions will be futile if we can't agree on the definitions of the very things we are talking about. For that reason, I think it's important to look at the legal definition of terms like: firearm, receiver, frame, and (PFM) privately made firearm.

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Important Preface—

Defining these legal terms isn't easy. As you'll see, this whole topic is quite confusing and I am certainly not a legal expert. I've tried to link to all source materials and taken text verbatim where appropriate.

This post won't answer every question pertaining to this topic, and really only addresses it from the federal level. That said, I hope this post provides some clarity on at least the legal language used for these topics and a starting point for you to research the topic even deeper.

Defining Terms—

To start, we can't just open up a webster's dictionary. We can't use a dictionary, because these terms have legal definitions found in statutory law. Then, the legislative branch interprets how the words of the law mean practically. Therefore, legal definitions often include various case rulings (case law) to cite how the court defined a particular term in a court decision.

We also need to be careful using colloquial terms. You know the conversation is going going off track when you try to correct a term used incorrectly, and they say something like “well you know what I mean.”

My point is, for people willing to exchange dialog respectfully on the guns, gun law, etc. topic, try to stick to terms that both sides can refer to. I've found this helps keep the discussion centered on facts and reality, rather than emotions and concepts, or how things ‘should be'.

Okay, enough of the intro, here are some definitions and the source.

Legally defining firearm—

For purposes of § 922 and § 924 violations 18 U.S.C. § 921(a)(3) defines a “firearm” as:

A. any weapon (including a starter gun) which will or is designed to or may readily be converted to expel a projectile by the action of an explosive;

B. the frame or receiver of any such weapon;

C. any firearm muffler or firearm silencer; or

D. any destructive device. Such term does not include an antique firearm.

This broad definition encompasses not only operable firearms but those that have been disassembled or dismantled or altered in such a way that they are inoperable at the time of the offense. For example, this definition has been found to include a firearm with the hammer filed down because it could be “readily converted” to expel a projectile. United States v. Ruiz, 986 F.2d 905 (5th Cir. 1993). This same justification applies for including starter guns within the definition of a firearm. “Firearm” is defined differently for violations of 26 U.S.C. § 5861. See 26 U.S.C. § 5845(a) and Appendix.

Now how this definition gets applied is really where it becomes confusing. The ATF proposed to change how they would interpret what the legislature meant in 18 USC 921(a)(3), to address ‘weapons parts kits‘. Here is what the accepted definition added to the Title 27 definition of firearm(s), as described in the executive summary:

In the NPRM, the Department proposed adding a sentence at the end of the definition of “firearm” in 27 CFR 478.11 to reflect existing case law, providing that “[t]he term shall include a weapon parts kit that is designed to or may readily be assembled, completed, converted, or restored to expel a projectile by the action of an explosive.” However, the proposed amendment was not intended to affect the classification of a weapon, including a weapon parts kit, in which the frame or receiver (as defined in the proposed rule) of such weapon is properly destroyed. See 86 FR at 27726, 27729-30. Therefore, another sentence was proposed to be added at the end of the definition of “firearm” to provide that “[t]he term shall not include a weapon, including a weapon parts kit, in which each part defined as a frame or receiver of such weapon is destroyed.” Id. at 27726.

The issue of defining the term ‘unfinished frame' is not new. Here is a podcast episode where we discussed the topic.

I've emphasized the text showing that the parts kits must be able to be readily converted to fit the firearm definition. Well, how is readily defined?

The Department proposed to add the term “readily” to 27 CFR 478.11 and 479.11 and define it as “a process that is fairly or reasonably efficient, quick, and easy, but not necessarily the most efficient, speedy, or easy process.” 86 FR at 27730, 27747, 27751. It further listed factors relevant in applying this proposed definition, such as time, ease, expertise, equipment, availability, expense, scope, and feasibility, with brief examples describing these factors. Id. The proposed definitions and factors are based on case law interpreting “may readily be converted to expel a projectile” in 18 U.S.C. 921(a)(3)(A) and “can be readily restored to shoot” in 26 U.S.C. 5845(b)-(d). See id. at 27730 & n.58. The NPRM explained that defining the term “readily” was necessary to determine when a weapon, including a weapon parts kit, a partially complete or damaged frame or receiver, or an aggregation of weapon parts becomes a “firearm” regulated under the GCA and NFA.

If you ask me, that an 80% lower that doesn't come with a complete part kit, tools, jig, etc wouldn't fit the legal definition. And according to this article, this is the reason Democrats in Congress are unhappy with the DOJ. The Democrats read this definition as including even unfinished 80% receivers that don't come with the parts and tools to readily convert it to a firearm. With this interpretation, you would need to pass a background check to purchase the unfinished 80% chunk of plastic that looks like a gun.

Legal Defining, Receiver and Frame—

Definition of frame or receiver in CFR 478.12 says:

(a) Except as otherwise provided in this section, the term “frame or receiver” means the following—

(1) The term “frame” means the part of a handgun, or variants thereof, that provides housing or a structure for the primary energized component designed to hold back the hammer, striker, bolt, or similar component prior to initiation of the firing sequence (i.e., sear or equivalent), even if pins or other attachments are required to connect such component to the housing or structure.

(2) The term “receiver” means the part of a rifle, shotgun, or projectile weapon other than a handgun, or variants thereof, that provides housing or a structure for the primary component designed to block or seal the breech prior to initiation of the firing sequence (i.e.,bolt, breechblock, or equivalent), even if pins or other attachments are required to connect such component to the housing or structure.

(3) The terms “variant” and “variants thereof” mean a weapon utilizing a similar frame or receiver design irrespective of new or different model designations or configurations, characteristics, features, components, accessories, or attachments. For example, an AK-type firearm with a short stock and a pistol grip is a pistol variant of an AK-type rifle, an AR-type firearm with a short stock and a pistol grip is a pistol variant of an AR-type rifle, and a revolving cylinder shotgun is a shotgun variant of a revolver.

(4) The following are nonexclusive examples that illustrate the above definitions:

CFR 478.12 is quite long, so I won't add it all, however here are a few illistration samples of common semi autos from the section.

(ii) Colt 1911, Beretta/Browning/FN Herstal/Heckler & Koch/Ruger/Sig Sauer/Smith & Wesson/Taurus hammer-fired semiautomatic pistols: The frame is the lower portion of the pistol, or grip, that provides housing for the sear.

(iii) Glock variant striker-fired semiautomatic pistols: The frame is the lower portion of the pistol, or grip, that provides housing for the sear.

(iv) Sig Sauer P250/P320 variant semiautomatic pistols: The frame is the internal removable chassis of the pistol that provides housing for the energized component (i.e., sear or equivalent).

Legally Defining, Privately Made Firearms (PMF)—

Historically, Americans could legally manufacture their own firearms for personal use. With the unfinished frame and received controversy, gun control advocates have zeroed in on this practice, and want to stop it.

The executive summary of 27 CFR 478.92, explains a privately made firearms as:

The NPRM proposed adding the term “privately made firearm” to 27 CFR 478.92 and to define it as a firearm, including a frame or receiver, assembled by a person other than a licensed manufacturer, and not containing a serial number or other identifying marking placed by a licensed manufacturer at the time the firearm was produced. See 86 FR at 27730. The term would not include a firearm identified and registered in the NFRTR pursuant to 26 U.S.C., chapter 53, or any firearm made before October 22, 1968 (unless remanufactured after that date).

I think it's important to note that privately manufactured firearms are still perfectly legal, here is the qualifying language from the executive summary of 27 CFR 478.92:

At the same time, nothing in the proposed rule restricted persons who are not otherwise prohibited from possessing firearms from making their own firearms without markings solely for personal use, nor did the proposed rule require individuals to mark PMFs when they occasionally acquire them for a personal collection, or sell or transfer them from a personal collection to unlicensed in-State residents in accordance with Federal, State, and local law. Further, the NPRM would not require FFLs to accept any PMFs, or to mark PMFs themselves, or to provide services to place identification marks on PMFs. Licensees would be able to arrange for individuals who wish to transfer PMFs to licensees to have them marked by another licensee before accepting them, provided they are properly marked in accordance with the proposed rule.

Gun Law and Self Defense Law—

Many of you reading this post carry a gun as a tool for self-defense. So I'll mention that there is an important distinction between gun law, and self defense law.

If you're interested in learning everything you need to know about self-defense law, check out this book called, Law of Self Defense Principles from one of the most respected authorities on the subject, Andrew Beanca. If reading isn't your thing, Andrew has video courses and a host of other great resources on his site, Law of Self Defense.

About Matthew Maruster

I follow my Lord and Saviour Jesus Christ who is the eternal co-equal Son of God. I currently live in Columbus, Ohio with my wife and daughter. I served in the Marine Corps Infantry. I was a Staff Sergeant and served as a Platoon Sergeant during combat in Iraq. After I was a police officer at a municipal agency in San Diego County. I have a Bachelors's Degree in Criminal Justice from National University. MJ Maruster Defense.


  1. BobF on November 11, 2022 at 2:12 pm

    Hey, enough legal mumbo jumbo – to the leftists and their useful idiots, guns are evil and scary – simple as that!


    • Alan on November 16, 2022 at 3:37 pm

      We have a federal Congress, U.S. House of Representatives and U.S. Senate maintained at significant expense to the nations taxpayers whose job is, among other things, the making or enactment of federal law. How is it that government agencies of departments, for instance the U.S. Department of Justice and BATFE, aka the ATF, have become law makers? Indeed, how did this example of political slight of hand ever come to pass?

  2. Johnny Eubanks on November 16, 2022 at 2:10 pm

    Guns are not evil or scary. It’s the person who has it in his or her hands and are using it for evil and scary purposes.

  3. Aaron on November 16, 2022 at 2:18 pm

    You guys need to update your information Supreme Court Justice said, and signed into law that FBI and ATF can no longer enforce a law based on frames and receivers for therefore it is constitutional to make these things. The law has not passed Supreme Court Justice says it’s unconstitutional for any agency law-enforcement to regulate what the definition of a frame or receiver is you guys need to update your stuff!!!

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