The honest answer is that there is no single authoritative list you can check. Massachusetts firearms law is layered, the layers were rewritten in 2024, the rewrite is on the November 2026 ballot, and the question of whether a particular firearm or accessory is lawful for you to possess depends on the interaction of federal law, state statute, statutory definitions that turn on physical features, an administrative roster maintained by the Executive Office of Public Safety and Security, and grandfather provisions that turn on dates of acquisition you may not be able to prove. A firearm that is lawful for your friend in Texas, lawful in Vermont, and lawful for a Massachusetts police officer can be a felony for you to possess across the river in Lowell.
This post explains the framework so that an educated buyer can navigate it. It is not a substitute for talking to a lawyer about a specific firearm before you put money down. The penalties for getting it wrong are serious: G.L. c. 269, § 10 carries a mandatory minimum 18-month sentence for unlicensed possession; G.L. c. 140, § 131M carries one to ten years for a first offense involving an assault-style firearm or large-capacity feeding device. There is no "I didn't know" defense that resolves these prosecutions.
The Four Overlapping Layers
Whether a particular firearm is lawful for you to possess in Massachusetts is determined by four overlapping bodies of law. Each layer can independently make a firearm illegal even if the others are clear. You have to clear all four.
Layer One: Federal NFA and § 922 Overlay
The federal National Firearms Act (codified in scattered sections of Title 26 and Title 18, with the principal civilian-conduct prohibitions at 18 U.S.C. § 922) regulates a category of items that includes machine guns, short-barreled rifles (SBRs, generally rifles with a barrel under 16 inches or an overall length under 26 inches), short-barreled shotguns, suppressors (also called silencers), destructive devices, and "any other weapons" as defined by ATF. Federal law allows civilian possession of most NFA items if you submit a Form 4, pay a tax, and obtain ATF approval (the "tax stamp").
Massachusetts is more restrictive than federal law on every single one of these categories. Three points matter for the buyer:
Suppressors are illegal in Massachusetts regardless of federal stamp. G.L. c. 269, § 10A makes it a state crime, punishable by up to five years in state prison, for a person who is not a federally licensed manufacturer or sworn law enforcement officer to sell, possess, or use any device designed to silence or muffle a firearm, including parts intended for use in assembling one. A federal Form 4 stamp does not authorize possession in Massachusetts. The federal government's permission to own the suppressor is independent of, and does not preempt, the state's prohibition. People are charged under § 10A every year for items they bought legally in another state.
Machine guns require a Massachusetts machine-gun license. G.L. c. 269, § 10(c) makes possession of a machine gun a state-prison felony unless the possessor holds permission under G.L. c. 140, § 131. The federal Form 4 is necessary but not sufficient. The same statute reaches sawed-off shotguns, automatic parts, bump stocks, rapid-fire trigger activators, and trigger modifiers, all of which are defined in G.L. c. 140, § 121.
Short-barreled rifles and shotguns sit in a more complicated zone. A federally registered SBR can in some circumstances be possessed by a Massachusetts LTC holder, but the analysis turns on whether the configuration also crosses into the assault-style firearm definition discussed below, and on the rifle and shotgun length definitions in § 121 (a "rifle" must have a barrel of 16 inches or more; a "shotgun" must have a barrel of 18 inches or more and an overall length of 26 inches or more; a "sawed-off shotgun" is defined in § 121 as a modified shotgun with a barrel under 18 inches or overall length under 26 inches and is reached by § 10(c)). Do not buy an SBR for Massachusetts use without specific legal advice on the configuration.
Layer Two: The G.L. c. 140, § 131M Ban
This is the layer that does the most work for ordinary buyers. G.L. c. 140, § 131M, as rewritten by St. 2024, c. 135 (H.4885), provides that "[n]o person shall possess, own, offer for sale, sell or otherwise transfer in the commonwealth or import into the commonwealth an assault-style firearm, or a large capacity feeding device." A first violation is punishable by a fine of $1,000 to $10,000 or by imprisonment of one to ten years, or both. A second violation is five to fifteen years.
The ban operates on two defined categories: "assault-style firearm" and "large capacity feeding device." Both terms are defined in G.L. c. 140, § 121.
Layer Three: The § 121 Definitions
This is the heart of the analysis. Whether a particular firearm is an "assault-style firearm" or a particular magazine is a "large capacity feeding device" turns on the statutory definitions, not on a manufacturer's marketing or on industry shorthand. The text is dense and was substantially restructured in 2024. The current operative definitions, verified against the malegislature.gov text, are:
Assault-style firearm. Section 121 defines an "assault-style firearm" through several alternative tests, any one of which is sufficient:
- Feature test for semiautomatic centerfire rifles (clause (a)): a semiautomatic, centerfire rifle that accepts a detachable feeding device and includes at least two of the following features: a folding or telescopic stock; a thumbhole stock or pistol grip; a forward grip, second handgrip, or protruding grip for the non-trigger hand; a threaded barrel designed to accommodate a flash suppressor or muzzle break or similar feature; or a shroud encircling all or part of the barrel designed to shield the bearer's hand from heat (excluding a slide that encloses the barrel). - Feature test for semiautomatic pistols (clause (b)): a semiautomatic pistol that accepts a detachable feeding device and includes at least two specified features, including the capacity to accept a feeding device that attaches outside the pistol grip, a second handgrip, a threaded barrel capable of accepting a flash suppressor or silencer, or a heat shroud. - Feature test for semiautomatic shotguns (clause (c)): a semiautomatic shotgun with at least two of: a folding or telescopic stock; a thumbhole stock or pistol grip; a non-trigger-hand protruding grip; or the capacity to accept a detachable feeding device. - Roster designation (clause (d)): any firearm listed on the assault-style firearm roster published under section 131¾ (the new section created by H.4885; discussed below). - Named-list test (clause (e)): any of the firearms specifically enumerated in the statute, "or copies or duplicates of these firearms, of any caliber," including AK-pattern rifles, UZI and Galil, Beretta AR70, Colt AR-15, FN/FAL, FN/LAR, FNC, the SWD M-10 series, Steyr AUG, INTRATEC TEC-9 and TEC-22, and revolving-cylinder shotguns including the Street Sweeper and Striker 12. - Copy-or-duplicate test (clause (f)): a firearm that was manufactured or configured to accept a detachable magazine and either has internal functional components substantially similar in construction and configuration to an enumerated firearm in clauses (d) or (e), or has a receiver that is the same as or interchangeable with the receiver of such an enumerated firearm. The statute carves out from clauses (d) and (e) any firearm "sold, owned and registered prior to July 20, 2016." - Exclusions (clause (g)): the term does not include manual bolt, pump, lever, or slide-action firearms; permanently inoperable firearms; certain antiques, relics, and theatrical props; firearms specified in the appendix to the federal 1994 assault-weapons ban as that appendix appeared on September 13, 1994; or semiautomatic shotguns that cannot hold more than five rounds in a fixed or detachable feeding device.
The practical takeaway: most modern semiautomatic rifles built on the AR-15 or AK platform are assault-style firearms by definition, even if no one calls them that on the box, because they accept detachable magazines and have at least two of the listed features. Adding or removing accessories (a folding stock, a flash hider, a vertical grip) can move a particular configuration in or out of the definition. The "copy or duplicate" language in clauses (e) and (f) is broad and reaches firearms that share receivers or major components with named platforms.
Large capacity feeding device. Section 121 defines this term to mean (i) a fixed or detachable magazine, belt, drum, feed strip, or similar device that has a capacity of, or can be readily converted to accept, more than 10 rounds of ammunition or more than 5 shotgun shells; or (ii) any part or combination of parts from which such a device can be assembled if those parts are in the possession or control of the same person. The definition excludes devices permanently altered to comply with the limit, attached tubular .22 rimfire devices, and tubular magazines on lever-action firearms or pump shotguns.
The 10-round threshold is hard. Standard-capacity magazines for many popular handguns (Glock 17, Sig P226, most full-size service pistols) are large-capacity feeding devices under this definition and are reached by the § 131M ban unless they qualify under the narrow grandfather provision discussed in the next section.
Large capacity firearm. Section 121 also defines a "large capacity firearm" as a firearm that is semiautomatic with a fixed large-capacity feeding device, semiautomatic and capable of accepting a detachable large-capacity feeding device when both are in the same person's possession or control in a vehicle, employs a rotating cylinder accepting more than 10 rounds (or more than 5 shotgun shells), or is an assault-style firearm. This definition matters for licensing (an LTC is required for any large-capacity firearm; an FID alone will not cover it) and for sentencing enhancements, but it is not itself a ban category. The ban category is § 131M.
Layer Four: The EOPSS Roster and the New Section 131¾
Massachusetts has long required, under G.L. c. 140, § 123, that firearms sold by licensed dealers in the commonwealth appear on a roster of approved firearms maintained by the Executive Office of Public Safety and Security (EOPSS). This is the "approved roster" that produced the Glock 19 controversy: a popular service pistol that was lawful to own if you already had it but that dealers could not legally sell new in Massachusetts because of testing-protocol issues with the roster process.
H.4885 added a new G.L. c. 140, § 131¾, which directs the secretary of public safety and security, with the advice of the firearm control advisory board established in § 131½, to "compile and publish a roster of assault-style firearms banned under section 131M and a roster of firearms approved for sale and use in the commonwealth." Section 131¾ requires the secretary to update both rosters at least three times per year, send copies to all licensed dealers, and to require licensing authorities to provide the rosters to permit and card holders.
In other words, the assault-style firearm roster referenced in § 121's definition of "assault-style firearm" (clause (d)) is a separate document from the legacy approved-for-sale roster, and both are now maintained under § 131¾. A buyer should check both rosters before purchasing any firearm in any gray zone. The rosters are administrative documents and they can change.
The Grandfather Provisions
Section 131M contains two narrow exceptions that often determine whether a particular item in a particular owner's hands is legal.
Subsection (b): assault-style firearms grandfather. Section 131M(b) provides that the ban "shall not apply to an assault-style firearm lawfully possessed within the commonwealth on August 1, 2024, by an owner in possession of a license to carry issued under section 131 or by a holder of a license to sell under section 122; provided, that the assault-style firearm shall be registered in accordance with section 121B and serialized in accordance with section 121C." Three conditions must all be met: lawful possession in Massachusetts on August 1, 2024; a then-current LTC or dealer license; and registration plus compliant serialization. An assault-style firearm acquired after August 1, 2024 (other than by a category-five exception, such as a qualified law enforcement officer under subsection (e)) is not grandfathered and possession is a § 131M violation.
Subsection (c): large capacity feeding devices grandfather. Section 131M(c) preserves possession of large-capacity feeding devices "lawfully possessed on September 13, 1994," but only with significant use-location restrictions. Possession is lawful only on private property the person owns or legally controls; on private property not open to the public with the owner's express permission; on the premises of a licensed dealer or gunsmith for repair; at a licensed firing range or shooting competition; or while traveling between these locations with the device unloaded and secured in a locked container per §§ 131C and 131L. Transfer is limited to an heir or devisee, an out-of-state resident, or a licensed dealer.
The September 13, 1994, date is unforgiving. If you cannot prove you possessed a particular magazine in Massachusetts on or before that date, the grandfather does not protect you. Receipts, photographs, dated correspondence, and similar documentary proof matter. A magazine you bought legally in New Hampshire in 2010 is not pre-1994 because you brought it into Massachusetts last year. The same goes for "I inherited this from my uncle who had it in the 80s," unless you can document the chain.
The Surrender Trap and Why It Matters Before You Buy
If you read nothing else in this post, read this: the moment your LTC is suspended or revoked, G.L. c. 140, § 129D requires you to "without delay, deliver or surrender to the licensing authority where the person resides all firearms or ammunition which are registered to the person or that the person then possesses." The licensing authority inventories what comes in. If any of the surrendered items are independently unlawful, the inventory becomes evidence of a separate crime.
The legal mechanics are these. The compelled § 129D surrender does not, by itself, immunize the surrenderer from prosecution for what was being possessed. Section 129D contains no immunity clause. So if the inventory turns up a non-grandfathered assault-style firearm (a § 131M violation), or a post-1994 large-capacity magazine the owner cannot prove pre-dates September 13, 1994 (also § 131M), or an NFA item without paperwork (potentially § 10(c)), or a firearm with an obliterated serial number (G.L. c. 269, § 11C, which carries 12 to 30 months and provides that possession of an untraceable firearm is "prima facie evidence" of guilt), the same surrender that the law required also produces the corpus of a separate criminal case. People have been charged with felonies for turning in firearms when their LTC was suspended. The mechanism is straightforward and prosecutors use it.
This is distinct from the statewide voluntary surrender program established under G.L. c. 140, § 131O, which does carry an immunity clause: that statute provides that "any citizen of the commonwealth who complies with the policies set forth by the colonel shall not be asked for identification and shall be immune from prosecution for possession of such firearm." Section 131O is the mechanism by which someone who finds an unlawful firearm in a deceased relative's house can turn it in to the state police anonymously without prosecution. G.L. c. 140, § 129C(a)(i) cross-references § 131O to permit possession for the limited purpose of effecting that surrender. None of those protections apply to a § 129D compelled surrender after an adverse LTC action. The two statutes operate in different worlds.
The practical consequence for a buyer: the unlawful magazine or unregistered AsF you tolerate in your safe today, while your LTC is current and no one is looking, becomes the evidence in a § 131M prosecution if anything ever causes your LTC to be suspended. And your LTC can be suspended for reasons that have nothing to do with firearms (a domestic 209A allegation, a misdemeanor charge, a mental-health hold under § 12). For more on the dynamics of trying to keep firearms when an LTC is challenged, see Can You Keep Guns During an LTC Appeal in Massachusetts?. The short version, applied to this post: the time to clean up your collection is before there is a problem, not after.
The November 2026 Wildcard
St. 2024, c. 135, the omnibus firearms reform that produced most of the framework described above, has been certified for the November 3, 2026, statewide ballot as a veto referendum. If the voters repeal H.4885, the statutory text in effect immediately before the law's October 2024 effective date returns. That earlier framework still banned "assault weapons" and large-capacity feeding devices, but used different definitions, different roster mechanisms, and different grandfather dates. The 2024 expansion of the definition of "assault-style firearm," the new § 131¾ roster process, the August 1, 2024 grandfather date in § 131M(b), the new licensing structure under § 121F, and several other features would unwind. The pre-H.4885 statutory regime would not be identical to a regulatory vacuum: the 2014 and 2016 frameworks would remain.
For a buyer in 2026, this matters in two practical ways. First, anything you buy today should be lawful under the current (post-H.4885) framework, because that is the framework being enforced. Second, if you are evaluating an item that is borderline under the current definitions, the referendum result will not retroactively cure a violation committed before the vote: the law that was in effect when you possessed the item is the law that applies to that possession. Do not buy in reliance on a possible repeal.
Practical Advice Before You Buy
I tell clients the same things, in the same order, every time:
Talk to a Massachusetts firearms attorney before you buy anything in a gray zone. This includes any modern semiautomatic rifle or pistol with two or more cosmetic features that resemble those in § 121's feature tests; any magazine with a capacity over 10 rounds; any NFA-class item; any "80% lower" or partially completed receiver or frame; any item described by the seller as "California compliant" or "featureless" (those builds are designed for a different statute and are not a safe harbor here); and anything described as a "build kit" or sold as parts. A 30-minute consultation costs less than the legal defense of a § 131M case.
Document the date and circumstances of every acquisition. Keep dated receipts. Keep the original packaging. Photograph items and their serial numbers. If you are claiming a pre-1994 magazine grandfather, you need contemporaneous documentation, not a story. If you are claiming a pre-July 20, 2016, copy-or-duplicate exclusion under § 121(f), the same is true. Without documentation, the grandfather may exist on paper but is unprovable in your case.
Confirm registration and serialization. Items that fall within the § 131M(b) grandfather are protected only if they are also registered under § 121B and serialized under § 121C. Check the Firearms Records Bureau registration. Check the serial number. If a firearm in your collection has a worn, defaced, or missing serial number, it is potentially an "untraceable firearm" under § 121 and its possession is a § 11C exposure separate from anything else.
Check both rosters. Before any purchase from a Massachusetts dealer, ask to see the EOPSS approved-for-sale roster entry for the specific make and model. If the firearm is not on that roster, the dealer is not supposed to sell it new in Massachusetts regardless of what is happening with assault-style status. Then check the assault-style firearm roster maintained under § 131¾. The rosters update at least three times a year.
Do not rely on the seller's representation. Out-of-state sellers regularly tell Massachusetts buyers, in good faith, that an item is "Massachusetts legal" because it is legal where they are. Massachusetts dealers occasionally make the same mistake. The criminal exposure runs against the possessor, not the seller. Verify independently.
If you already own something you are not sure about, do not surrender it to police "to be safe." That is the § 129D trap discussed above. The lawful path is either confirming the item's legal status (and properly registering and serializing it if it qualifies for the § 131M(b) grandfather), lawfully transferring it to an out-of-state resident or a licensed dealer through the procedures in § 128A and § 131M(c) where applicable, or, where appropriate, surrendering it through the § 131O voluntary surrender program with its immunity protection. A lawyer can help you choose the right path before you create evidence against yourself.
If you have questions about whether a specific firearm is legal for you to possess in Massachusetts, or about cleaning up an existing collection before a problem arises, contact my office.