gunsnprices/firearm-calibers

Firearm & Ammunition Calibers

A clean dictionary of the firearm calibers (cartridges) that are actually sold by US online retailers, with the spellings retailers use for each one. Built and maintained by GunsNPrices, a price comparison site for guns and ammo.

Use it to normalize messy caliber fields in product feeds, to group listings by caliber, or as a reference list of cartridges in current US retail.

As of 2026-10-12: 293 calibers, 326 retailer spellings, 34 caliber pairs, built from 63,930 gun and ammo listings across 40 US stores.

Files

calibers.csv (also calibers.jsonl)

Column	Meaning
id	Stable lowercase id, e.g. 9x19mmparabellum
name	Display name, e.g. 9×19mm Parabellum, .30-06 Springfield
type	handgun, rifle, rimfire, shotgun, airgun or muzzleloader
aliases	Spellings retailers use for this caliber, separated by | (a list in the JSONL file)
products_guns	Firearm listings chambered in this caliber on GunsNPrices
products_ammo	Ammunition listings in this caliber
products_in_stock	Listings in stock at one or more stores on the build date
ammo_url	GunsNPrices page comparing ammo prices for this caliber, if one exists
guns_url	GunsNPrices page comparing gun prices for this caliber, if one exists
site_name	The exact value used in GunsNPrices filters

caliber_pairs.csv

Calibers that retailers list together on one product, such as rifles marked .223 Rem/5.56×45mm NATO or revolvers that take both .357 Mag and .38 Special. listings is the number of products with that combined marking.

caliber_a	caliber_b	listings
.223 Rem	5.56×45mm NATO	1,141
.308 Win	7.62x51mm NATO	990
.357 Mag	.38 S&W Special	129
.22 LR	.22 WMR	81
.410 Bore	.45 Colt	67

A pair means "listed together", not "safe to interchange". Always follow the markings on the firearm and the ammunition maker's guidance.

How it was built

1. Calibers are the values used in the caliber filter of gunsnprices.com.
   • Junk values like MULTI or All Calibers are dropped, and so are bare bore diameters such as .355 or 6mm.
   • Pressure variants (+P) are folded into the base caliber.
   • Combined markings are split into single calibers and kept in caliber_pairs.csv.
2. Aliases come from about 6,000 raw caliber strings seen in retailer data that our team mapped by hand. For this public list only high-confidence spellings were kept, and 3,374 were rejected. A spelling is kept only when:
   • it appears at two or more stores;
   • its numbers agree with the caliber (556 NATO → 5.56×45mm, 30-06 → .30-06 Springfield);
   • it contains no barrel lengths, round counts, loads or model names;
   • it does not name a different cartridge or maker (.22 Long is not .22 LR, 223 Win is not .223 Rem);
   • a bare number is kept only when one caliber clearly dominates it (9mm → 9×19mm Parabellum, but not .38 or 300).
3. Type comes from the store categories where the guns and ammo are listed, with a few manual fixes.

Example

import pandas as pd, re

cal = pd.read_csv("hf://datasets/gunsnprices/firearm-calibers/calibers.csv")

def key(s):
    s = s.lower().replace("×", "x")
    s = re.sub(r"(?<=\d)\.(?=\d)", "#", s)
    return re.sub(r"[^a-z0-9#]+", "", s).replace("#", ".")

lookup = {}
for _, r in cal.iterrows():
    for v in [r["name"], r["site_name"]] + (r["aliases"].split(" | ") if isinstance(r["aliases"], str) else []):
        lookup[key(v)] = r["name"]

print(lookup[key("556 NATO")])         # 5.56×45mm NATO
print(lookup[key(".45 Long Colt")])    # .45 Colt

Limitations

• US retail only. Military and obsolete cartridges that aren't sold online in the US are mostly missing.
• Counts are a snapshot of one day. They show what is listed, not what is popular.
• The alias list favors precision over coverage, so many calibers have no aliases yet.

License and attribution

CC BY 4.0. Credit GunsNPrices (gunsnprices.com) with a link when you use or republish this data.

Updates and contact

• Rebuilt from live catalog data when the dictionary changes.
• Corrections and missing spellings: app@gunsnprices.com.
• Live price comparison for every caliber: gunsnprices.com.