Are M16 Bolts Legal? What Buyers Need to Know

Are M16 bolts legal? Yes — for most people in most states, owning an M16 bolt or bolt carrier group is perfectly legal, because the bolt itself is not the part federal law treats as a machinegun. The regulated component is the auto sear, and that is where the law draws a hard line.

That distinction trips up a lot of buyers. You can order a full-auto-profile M16 bolt carrier from a major parts supplier, have it shipped to your door, and never break a single rule. Buy or make the wrong sear, though, and you are facing serious federal charges.

This guide walks through exactly which parts are legal, which are not, how the 1986 cutoff works, what state laws add on top, and the mistakes that land well-meaning people in trouble — so you know precisely where you stand before you spend a dollar.

Are M16 Bolts Legal: The Short Answer

Yes, M16 bolts and bolt carrier groups are legal to buy and own in the United States for most civilians. Under federal law, the bolt and bolt carrier are ordinary firearm parts, not machineguns, and they can be shipped directly to your home with no FFL transfer required. The part federal law actually regulates is the auto sear (sometimes called the drop-in auto sear or DIAS), which converts an AR-15 into a machinegun. A genuine M16 auto sear manufactured after May 19, 1986 cannot be transferred to private citizens at all; sears made before that date are transferable only through the ATF's National Firearms Act process with a tax stamp, dealer involvement, and months of paperwork.

So the practical answer is layered. The bolt: legal everywhere that AR-15s are legal. The carrier: legal, including full-auto-profile carriers. The sear: heavily restricted or banned. State law adds another layer — California, New York, New Jersey, and a handful of others restrict so-called assault weapons and certain parts, so the same bolt that ships freely to Texas may face restrictions elsewhere. Rules also vary by state and are updated periodically, so confirm current details with the ATF and your state's attorney general or state police before buying.

What Exactly Is an M16 Bolt (and What Makes It Different)

The M16 bolt assembly has three main pieces: the bolt itself, the bolt carrier, and the firing pin, cam pin, and retaining pin that hold it together. On a semi-auto AR-15, the carrier has a shorter internal profile with a shallow cut at the rear. On an M16, the carrier is full-profile — the rear is solid, with no lightening cut — so it can trip a sear during the cycle and fire again automatically.

Here is the part that confuses people: the full-auto carrier is legal, but it does not make a rifle full-auto. The carrier is just a shaped piece of steel. It needs an auto sear (and the sear trip on the carrier, plus a selector) to function as a machinegun. That is why the ATF treats the sear — the actual fire-control device — as the regulated component, while the carrier remains an uncontrolled spare part.

Practical differences worth knowing if you are shopping:

• Weight: full-auto carriers run noticeably heavier than semi-auto carriers, which many shooters prefer for smoother cycling.
• Compatibility: a full-auto-profile carrier drops into any standard AR-15 and works fine in semi-auto.
• Markings: genuine Colt M16 carriers are stamped with an M or MP mark; aftermarket carriers are unmarked or differently marked.

None of these features changes the legal status of the bolt or carrier. The sear is the line. (See Also: Are Htc Bolt and Htc 10 the Same Phone)

The Legal Line: Which M16 Parts Are Regulated

Federal law defines a machinegun under the National Firearms Act as any weapon that fires more than one shot per trigger pull — and, critically, the definition includes the parts designed and intended to convert a weapon into a machinegun. The ATF has long taken the position that the auto sear is the machinegun itself. Possess an unregistered sear, even with no rifle attached, and you legally possess an unregistered machinegun.

The Firearm Owners Protection Act of 1986 froze the civilian market. Machineguns and their sears manufactured after May 19, 1986 may only be transferred to government agencies, dealers with special occupational tax status, and manufacturers. Pre-1986 transferable sears exist in fixed numbers, which is why registered sears routinely sell for tens of thousands of dollars at auction.

Where other parts fall:

• Bolt and bolt carrier: unregulated at the federal level; sold openly.
• Full-auto hammers and selectors: generally sold as parts, though combining them with other components can create legal exposure depending on ATF interpretation.
• Auto sear (complete): a machinegun under the NFA — registration or prohibition applies.
• Partial sear parts (e.g., a drilled or unfinished sear body): the ATF has treated certain easily-completed parts as machineguns. This is a genuinely gray and dangerous area; do not assume a partial part is legal.

Because ATF interpretations shift and state law stacks on top, treat this section as a practical guide and verify the current position with the ATF directly before relying on any specific part's status.

M16 Parts Compared: What You Can and Cannot Own

Shopping for M16-related parts gets confusing because retailers list everything side by side with no legal labels. This table breaks down the common parts, their federal status, and who each option actually suits.

The takeaway: everything in the top half of the table is ordinary commerce. The bottom half is where licensing, cost, and criminal exposure live. If a seller is vague about what a part does or hints it will "open" something, walk away — ambiguity in this market is a warning sign, not a bargain.

How to Buy an M16 Bolt Carrier Legally

Buying the legal parts is straightforward, but doing it in the right order protects you. Follow these steps:

1. Confirm your state allows AR-15 parts. Check whether your state restricts assault-weapon features or specific components. A few states scrutinize parts, not just complete rifles.
2. Buy from a known dealer. Established retailers (Brownells, MidwayUSA, Primary Arms, and similar) vet their inventory. Random marketplace listings for "M16 parts lots" are where problems start.
3. Know what you are ordering. A "full-auto profile carrier" or "M16 BCG" is legal. A listing for a sear, sear trip, or "conversion kit" is not something a civilian should order.
4. Keep your receipt. A dated invoice showing you bought a legal carrier is cheap insurance if questions ever arise.
5. Do not modify the part. No drilling, no machining, no pairing it with questionable components. Modification is where legal possession becomes illegal manufacture.
6. Inspect on arrival. Check headspacing with proper gauges if you are pairing a new bolt with a used barrel — that is a safety issue, not a legal one.

For an NFA sear transfer, the process is different: find a Class 3 dealer, complete ATF Form 4, pay the $200 transfer tax, submit fingerprints and photographs, and wait for approval before the part can be yours. Approval times have varied from several months to over a year, so plan accordingly. (See Also: Are Ls Rod Bolts Reusable)

Key Factors That Change the Answer

Federal law sets the floor, but several factors can flip the answer from "legal" to "felony" or from "legal" to "restricted."

• Your state. California, New York, New Jersey, Massachusetts, Connecticut, Hawaii, and others restrict assault weapons and some parts. New Jersey in particular has prosecuted possession of unregistered machinegun parts aggressively. A part legal under federal law can still be illegal under state statute.
• What else you own. A full-auto carrier in a drawer is a spare part. The same carrier installed alongside a sear in a receiver changes the analysis entirely. Context matters to prosecutors and the ATF.
• Intent and modifications. Machining a carrier, drilling a sear body, or owning conversion documentation alongside parts can support a charge of intent to manufacture a machinegun.
• Manufacture date of the sear. Only pre-May 1986 sears are even theoretically transferable, and only if they were properly registered at the time.
• Local ordinances. A handful of cities and counties layer their own rules on top of state law.

The pattern is consistent: the bolt and carrier stay legal across nearly all these variables, while anything touching the sear or a conversion path does not. If your situation involves any of the factors above — especially living in a restrictive state — a quick call to a firearms attorney or your state police firearms unit costs nothing and prevents everything.

Common Mistakes That Get People in Trouble

Most people charged with machinegun offenses are not criminals by intent — they made one avoidable error. These are the patterns that show up repeatedly:

• Buying "parts kits" from overseas. Demilled M16 kits sometimes arrive with a sear or sear parts included. Possessing that sear, even as "just a souvenir," is unregistered machinegun possession.
• 3D printing or machining a sear. Manufacturing an auto sear is manufacturing a machinegun. The ATF has pursued these cases actively, and the penalty structure is severe.
• Assuming "it's just a carrier, so anything goes." True for the carrier alone — false once it is combined with a sear or selector in a way designed to fire automatically.
• Skipping the state-law check. Federal legality is not a shield against state charges. People moving from Arizona to New Jersey with a parts bin learn this the hard way.
• Trusting forum advice. Anonymous posts about "gray area" builds are not legal guidance, and neither is this article — verify with the ATF or an attorney for your specific facts.

The safe rule is simple: buy bolts and carriers from reputable dealers, never touch sears or conversion parts, and never modify anything. That rule keeps you on the legal side of every line discussed here, in every state where AR-15 ownership itself is permitted.

Troubleshooting and Special Situations

Real life produces scenarios the basic rules do not obviously cover. Here is how the common ones shake out:

• You inherited a parts bin with an unknown sear. Do not keep it, sell it, or transport it. Contact the ATF directly and ask how to surrender it — voluntary surrender of an unregistered sear is handled far differently than discovery during a search.
• You are moving to a restrictive state. Check the destination state's laws before the move, not after. Some parts legal in your current state may need to be sold, surrendered, or registered under the new state's scheme.
• You want to sell a full-auto-profile carrier. Selling the carrier itself is generally fine under federal law to a buyer in a state where it is legal. Do not ship it with any sear, selector, or documentation suggesting conversion.
• Your carrier has a sear trip and you are worried. The trip on a full-auto-profile carrier is standard and legal. The carrier alone does not enable automatic fire.
• A listing looks too good. A "complete M16 fire control group" for a low price is either mislabeled, illegal, or a sting. All three outcomes are bad.

When in doubt, the two reliable resources are the ATF's own publications and a licensed firearms attorney. Everything else — forum posts, YouTube videos, a buddy's confident opinion — is hearsay with consequences attached.

Common Questions About M16 Bolt Legality

Can I Own an M16 Bolt Carrier Group in a State with an Assault Weapons Ban?

In most cases yes, because carriers are spare parts, not firearms, and most bans target complete rifles and specific features. However, a few states scrutinize parts, and local ordinances can add restrictions. Check your state's statutes or call the state police firearms unit before ordering, since these laws change and enforcement varies.

Does a Full-Auto Bolt Carrier Make My Ar-15 Full-Auto?

No. The carrier is a shaped piece of steel with no fire-control function on its own. Automatic fire requires an auto sear, a full-auto selector, and a receiver machined to accept them. A full-auto-profile carrier in a standard semi-auto AR-15 simply cycles the action slightly heavier and smoother than a semi-auto carrier. (See Also: Are Jeep Flexplate Bolts Reuseable)

Why Are Full-Auto Bolt Carriers Sold Openly If M16s Are Banned?

Federal law regulates the machinegun and its conversion device — the sear — not every component that happens to appear in a full-auto rifle. The ATF treats the carrier as an ordinary part because it cannot fire automatically by itself. That is the same logic that allows M16-pattern barrels, buffers, and furniture to be sold without restriction.

Is It Legal to Buy a Drop-in Auto Sear?

Only through the NFA process, and only if the sear was manufactured and registered before May 19, 1986. Post-1986 sears cannot be transferred to private citizens at all. Registered pre-1986 sears require a Form 4, a $200 tax, a Class 3 dealer, and approval, and they typically cost tens of thousands of dollars.

Do I Need an Ffl to Buy an M16 Bolt?

No. Bolts, bolt carriers, and bolt carrier groups are not firearms under federal law, so they ship directly to your door with no background check or transfer, just like triggers, handguards, or barrels. The same is true in most states, though a handful restrict certain parts, so verify locally.

What Happens If I'm Caught with an Unregistered Auto Sear?

Possession of an unregistered machinegun is a federal felony carrying up to ten years in prison and substantial fines, and it applies even if the sear is never installed in a rifle. State charges may stack on top. If you discover one, contact the ATF about voluntary surrender rather than keeping or selling it.

Are M16 Bolts and Ar-15 Bolts the Same Part?

The bolt itself is basically identical — same dimensions, same locking lugs. The difference is the carrier: the M16 carrier has a full-length rear profile with a sear trip, while semi-auto carriers have a shorter, cut-down rear. They are interchangeable in standard receivers, which is why the full-auto-profile carrier is a popular upgrade for reliability.

Final Verdict

So, are M16 bolts legal? Yes — the bolt and bolt carrier group are ordinary, unregulated parts under federal law, and you can buy them from any major dealer without an FFL, background check, or paperwork. The legal line sits at the auto sear, which is treated as the machinegun itself.

Keep the rules straight: buy bolts and carriers freely, never purchase or make a sear unless you are going through the full NFA process on a registered pre-1986 unit, and never modify anything. State law can add restrictions, so confirm the current rules with the ATF and your state's firearms authority before buying.

Follow those boundaries and owning an M16-pattern bolt carrier is one of the simplest, lowest-risk upgrades in the AR-15 world.