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FN America
Overview
The FN AR-15 M16 Barrel is an 18-inch, M4 profile barrel designed for optimal performance with 5.56 NATO ammunition. Featuring a rifle-length gas system with a .750 gas block diameter, this barrel is tailored for reliable cycling and accuracy, while its 1:8 twist rate provides versatility in stabilizing a range of bullet weights. This barrel is commonly found in builds that prioritize a rifle-length gas system and utilize 5.56 NATO caliber, making it a solid choice for precision and reliability.
Specifications
Available Merchants(7)
Prices checked
Price Alert
October 2026 on GunPartPicker
FN America FN AR-15 M16 Barrel 18 Rifle Length 5.56mm ranked #52 of the 329 barrels builders added on GunPartPicker in October 2026. Builders have added it to their builds on GunPartPicker. Since April 2026, it ranks #49 of the 1,046 barrels builders have added. Builds with this barrel are nearly all chambered in 5.56 NATO, nearly all on rifle-length gas, and nearly all AR-15.
It was in stock most times we checked in October 2026, and today 6 of the 7 retailers we track have it in stock. The best price drifted down from $279 to $226.49 over October 2026 without a real sale. Buying today, the lowest price is $234.26 at KY Gun Company.
Updated · from real builds on GunPartPicker · Prices checked · refreshed daily across 37 retailers
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Read the guide: AR-15 Barrel Length & Brand Report →Check it against the live catalog:
Frequently Built With
The part most often added in each category by the builds that include this one
Geissele Automatics AR-15 16 Super Duty Stripped Upper Receiver Ddc
Breek Arms AR-15 Warhammer MOD2 Ambidextrous Charging Handle Black
Bravo Company M16 Bolt Carrier Group Black
Griffin Armament MK2 Ambi Stripped AR-15 Lower Receiver - Ambidextrous Controls - Flared Magwell - Anodized Black - MK2AL
WMD Guns AR-15 Gas Tube Nitromet Rifle
Spike's Tactical Crr Quad Rail AR-15 Handguard - 15"
Builds Featuring This Part
See all builds →Builds in the community that include the Fn Ar-15 M16 Barrel 18 Rifle Length 5.56mm
| Build | Parts | Total |
|---|---|---|
 | 28 | $3493.73 |
 | 25 | $3008.19 |
 | 10 | $906.72 |
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