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How to Identify Your Shotgun: Remington 870, Mossberg 500 & More

A black pump shotgun behind the door, a pair of old double barrels over the fireplace, an heirloom you've never actually looked at closely — shotguns are some of the most common firearms to inherit, and some of the least understood. Unlike a rifle or pistol, the number that matters most on a shotgun isn't a caliber. Here's how to read one correctly.

Read this before you touch the trigger

Treat every shotgun as loaded until you have personally opened the action and confirmed it is clear. This matters more with shotguns than almost any other type of firearm because of one specific hazard: many older double-barrel shotguns were built with Damascus or twist-steel barrels, made by forge-welding thin ribbons of iron and steel around a mandrel. They were made for the low-pressure black-powder loads of their era and were never designed for modern smokeless ammunition. Firing standard shells through a genuine Damascus barrel can split or burst it. If you have an older double-barrel and are not certain of the barrel steel, have a gunsmith inspect it before anyone loads a shell.

1. The gauge stamp -- the number that actually matters

A shotgun's bore size is measured in gauge, not caliber (with one exception noted below), and it is stamped directly on the barrel, usually on the flat near the chamber. Confirm this before assuming anything about the gun.

• 12 gauge: by far the most common size in American hands, for hunting, clays, and defense alike.
• 20 gauge: the next most common -- smaller, lighter recoil, popular for upland hunting and as a first gun for younger or smaller-framed shooters.
• .410 bore: the odd one out -- this is actually measured as a caliber (the bore diameter in decimal inches) rather than a gauge, which is why the number looks so different. Small and light-kicking, common in youth and small-game guns.
• 16 gauge and 28 gauge: less common today but far from rare on older or specialty guns -- both have devoted followings and their own ammunition, which can be harder to find locally.

Next to the gauge you'll usually find a chamber length stamp -- typically 2 3/4", 3", or 3" Magnum on 12-gauge guns. This matters for more than trivia: firing a shell longer than the chamber is rated for is unsafe. Always match the shell to the chamber stamp, not just the gauge.

2. Sort the action type

• Pump-action: a sliding forend racks the next shell. This is the most common inherited or pawn-shop shotgun by a wide margin -- the Remington 870 (over 11 million made, the best-selling shotgun in American history) and the Mossberg 500 family dominate this category, with the Winchester Model 12 and Ithaca 37 as older, sought-after classics.
• Semi-automatic: fires one shot per trigger pull and cycles itself, no pump or lever needed. The Remington 1100/11-87, Browning A5, and various Benelli models are the names you'll see most.
• Break-action: the barrel(s) pivot open at a hinge to load, like a classic hunting gun. This covers both side-by-side doubles (barrels next to each other) and over/under doubles (stacked), plus simple single-shot break-actions. This is the category where genuine antiques and family heirlooms most often turn up.

3. Remington 870 vs. Mossberg 500: the safety tells you everything

These are the two shotguns people confuse most often -- both are black pump-actions with a similar silhouette, and either one is a completely reasonable guess for "the pump shotgun in the closet." One glance at the safety settles it.

• Remington 870: the safety is a small cross-bolt button behind the trigger guard -- push it from one side to the other. The receiver is roll-marked "Remington 870" (or the specific model, e.g. "870 Express," "870 Wingmaster") on the left side.
• Mossberg 500 (and 590/835): the safety is a sliding tab on top of the receiver, right behind where the hammer would be, thumb-operated front-to-back. This top-mounted safety is the single fastest way to identify a Mossberg pump at a glance, even from across a room. The receiver reads "Mossberg 500" (or 590, 835) on the left side.

Both are enormously common, reliable, and widely parts-supported -- neither one is the "better" gun, they're just built differently, and that safety placement is the fastest tell in the field.

4. Older doubles: makers, chokes, and the Damascus check

If what you've got is an old side-by-side or over/under, the maker's name is usually engraved or stamped on the rib (the flat strip between or above the barrels) or the receiver. American makers like Parker, L.C. Smith, A.H. Fox, and Ithaca made genuinely valuable doubles that collectors actively seek -- condition, engraving level, and original barrels all drive value significantly. Many other older doubles are humbler "trade guns" or imported hardware-store guns worth far less, but every one deserves the same barrel-steel check before firing.

• Look for "Damascus," "Twist Steel," or a wavy/ribbon pattern in the barrel finish itself -- this is the clearest sign of forge-welded barrels not rated for modern ammunition.
• Fixed chokes on older barrels are usually marked with notches near the muzzle (a system of small cuts indicating Cylinder, Improved Cylinder, Modified, or Full choke) rather than the screw-in choke tubes common on modern guns.
• When in doubt, don't fire it. A gunsmith can confirm barrel steel and safe loads in a few minutes -- cheap insurance against a very expensive mistake.

Quick-reference: what each detail tells you

For deep, maker-by-maker detail on American double guns -- Parker grades, Fox frame sizes, Damascus dating -- the standard collector reference most double-gun owners eventually pick up is a dedicated double-barrel shotgun identification guide.

Disclosure: GoBallistic earns a small commission when you buy through the link above, at no additional cost to you. Helps keep the app free.

So what's behind the door?

Start with the gauge and chamber stamp on the barrel -- that's the foundational fact everything else builds on. Then sort pump, semi-auto, or break-action by how it cycles, and if it's a pump, let the safety location settle 870 versus Mossberg in one glance. If it's an older double, the maker's name and a careful look at the barrel steel matter more than almost anything else about the gun.

If this shotgun came to you with no story attached at all, our guide to identifying an inherited firearm walks the full process end to end, and if it's a military-marked surplus piece rather than a hunting gun, the surplus markings guide covers arsenal stamps and import marks.