Massachusetts bans almost all possession of large capacity magazines, which the law calls “large capacity feeding devices.” A magazine that holds more than 10 rounds can lead to a felony charge under two statutes: G.L. c. 140, § 131M, rewritten by the 2024 gun law, and G.L. c. 269, § 10(m). Either one carries up to 10 years in state prison for a first offense. The definition, the narrow exceptions, and whether you knew what the magazine could hold often decide these cases.
At a Glance: Large Capacity Magazines
Felony
both statutes carry state prison
Up to 10 years
first offense under either statute
More than 10 rounds
or more than 5 shotgun shells
No CWOF, no file
for a § 10(m) charge
The law: G.L. c. 140, §§ 121 and 131M; G.L. c. 269, § 10(m)
What Counts as a Large Capacity Feeding Device
Under G.L. c. 140, § 121, a large capacity feeding device is:
- “a fixed or detachable magazine, belt, drum, feed strip or similar device that has a capacity of, or that can be readily converted to accept, more than 10 rounds of ammunition or more than 5 shotgun shells”; or
- “any part or combination of parts from which a device can be assembled if those parts are in the possession or control of the same person.”
The definition does not include:
- a device “permanently altered so that it cannot accommodate more than 10 rounds of ammunition or more than 5 shotgun shells”;
- an attached tubular device that operates only with .22 caliber rimfire ammunition; or
- a tubular magazine in a lever-action firearm or on a pump shotgun.
The Two Statutes
G.L. c. 140, § 131M. The 2024 gun law (Acts 2024, c. 135, § 71) replaced this section. It now says: “No 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.”
G.L. c. 269, § 10(m). This section punishes anyone “who knowingly has in his possession, or knowingly has under his control in a vehicle, a large capacity firearm or large capacity feeding device therefor who does not possess a valid license to carry firearms.” A firearm identification card “shall not be a defense.”
What the Commonwealth Must Prove Under § 10(m)
Under the model jury instruction, the Commonwealth must prove beyond a reasonable doubt that:
- You possessed the item, or had it under your control in a vehicle.
- The item met the legal definition of a large capacity feeding device.
- You did not have a valid license to carry.
- You knew the device met the legal definition of “large capacity,” or knew it could hold more than 10 rounds or more than 5 shotgun shells. Commonwealth v. Cassidy, 479 Mass. 527 (2018).
Possession can be actual or constructive. See constructive possession.
Penalties
§ 131M(d):
- First offense: a fine of $1,000 to $10,000, 1 to 10 years in prison, or both.
- Second offense: a fine of $5,000 to $15,000, 5 to 15 years in prison, or both.
§ 10(m):
- 2½ to 10 years in state prison.
- The sentence “shall not be reduced to less than one year, nor suspended,” and there is no probation, parole, furlough, work release, or good-conduct deduction until that minimum is served.
- A person who holds a valid firearm identification card “shall not be subject to any mandatory minimum sentence” under § 10(m).
- A § 10(m) prosecution “shall neither be continued without a finding nor placed on file,” and pretrial probation under G.L. c. 276, § 87 does not apply to anyone 18 or older.
Both statutes carry state prison, so both are felonies. See the difference between misdemeanors and felonies.
Exceptions
Pre-1994 devices (§ 131M(c)). The ban does not apply to devices “lawfully possessed on September 13, 1994,” but only while the device is:
- on private property the possessor owns or legally controls;
- on private property not open to the public, with the owner’s express permission;
- at a licensed dealer or gunsmith for lawful repair;
- at a licensed firing range or sports shooting competition venue; or
- traveling to and from those places,
and only if it is “stored unloaded and secured in a locked container” under §§ 131C and 131L. Such a device may be transferred only to an heir or devisee, a person residing outside Massachusetts, or a licensed dealer.
Law enforcement and manufacturers (§ 131M(e)). As amended effective August 5, 2025 (Acts 2025, c. 14, § 45), § 131M does not apply to qualified or qualified retired law enforcement officers under the federal Law Enforcement Officers Safety Act; officers currently certified by the POST Commission whose certification is not suspended, limited, or restricted; law enforcement agencies; and federally licensed manufacturers selling out of state or for export.
§ 10(m) exemptions. Section 10(m) does not apply to authorized government employees, law enforcement, and military members acting within the scope of their duties; public historical societies, museums, and institutional collections; or federally licensed gunsmiths.
Defenses
- Not a large capacity device. The Commonwealth must prove capacity. A permanently altered magazine, a .22 rimfire tubular device, or a lever-action or pump-shotgun tubular magazine is excluded.
- No knowledge. Under § 10(m), the Commonwealth must prove you knew the device was large capacity or could hold more than 10 rounds.
- No possession. Being near a magazine, or in a car or home where one is found, does not by itself prove possession.
- An exception applies. Pre-1994 possession under the conditions in § 131M(c), or a listed law enforcement or professional exemption.
- Unlawful search. If the magazine was found in an unlawful search, it may be suppressed. See challenging a search.
Why a Lawyer Matters
A magazine charge can mean a felony record and, under § 10(m), a mandatory minimum with no CWOF or filing. The definition, the knowledge requirement, and the exceptions are technical, and each one can decide the case. In 23 years of defending clients in Massachusetts courts, I have handled many firearm cases. If you have been charged, contact my office or call 781-393-5900.
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Disclaimer
This article is for general educational information about Massachusetts criminal law. It is not legal advice for your situation, and reading it does not create an attorney-client relationship. Laws change. For advice about a specific case, speak with a licensed Massachusetts attorney.
